[fix] Deprecation warnings

See merge request !28

[id] Initialize the free id counter!

See merge request !26

add support for dune-corepy

See merge request !25

Minor changes

See merge request !24

I do not use the DGF format, but users having to include the
implementation in `dgffoam.cc` looks wrong.

The file was removed in a3cdfb27

It only contained the default program generated by duneproject.

[refelement] Get copies as references are deprecated upstream

See merge request !23

Use unique IDs for all entities no matter which codim

Closes #9

See merge request !22

Id sets have to provide unique ids for all entitites of a grid.
In Foamgrid the id was only unique within the subset of entities
of the same codimension.

added std:: in front of array, fixes issue #8

Closes #8

See merge request !21

integer types in interface cleaned up

See merge request !20

integer types in interface cleaned up, to reduce warnings related to comparison between signed and unsigned integers

Fix indexInOutside method for leaf intersections in adaptive grids

Closes #4

See merge request !17

The previous test refined all elements using local adaptivity. The new
test results in a leaf view with elements of different levels and tests
more things. The bug fixed in 6e374b7d
would have been revealed.

The previous implementation had a sign mistake and thus only worked
for intersections connecting elements on the same level. The new
implementation works for adaptive grids as well.

The core module versions used to be 3.0, but have recently been lowered
to 2.6.  As a consequence, dune-foamgrid would not accept them anymore,
considering them 'too old'.

[tuple] Use std::tuple directly everywhere

Remove deprecated Dune tuples header and use std::tuple directly everywhere where it wasn't done yet.

See merge request !16

Feature/growth insertion index

Feature request
*****************
* Each element has a` growthInsertionIndex` that can be queried using a grid method with the same name.
* This index is only valid between calling `grow()` and `postGrow()` and only for elements that have been inserted using the grids `insertElement` method.
* It can be used to attach user data to an element inserted with the `insertElement` method, because we don't know at insertion time (before calling `grow()`) which index or id the element will have in the grid. 
* The concept is very similar to the `insertionIndex` of the factory with the difference that the validity of the index is only temporary.

I'm open to any suggestion how to make this better or also renaming of the interface function.
Without this it's impossible to attach data to a newly created element at creation time, i.e. it's impossible to distinguish between new elments that were inserted together using insertElement().

This branch is based on !14 

See merge request !15

Bugfix/double vertex insertion

When inserting two element that share a new vertex this vertex was inserted twice
resulting in a disconnected grid. The check if a vertex is already inserted was
already in place, however the map had the wrong scope and the pointer written
in the map was a pointer to the grid entity not the entity in the to-be-inserted queue.

See merge request !14

Note: this is a backward compatible change. The growth insertion index
can now be used conveniently to attach user data to the new element.

Each element has a growthInsertionIndex that can be queried using a grid method
with the same name. This index is only valid between calling grow() and postGrow()
and only for elements that have been inserted using the grids insertElement method.
It can be used to attach user data to an element inserted with the insertElement method,
because we don't know at insertion time (before calling grow()) which index or id
the element will have in the grid. The concept is very similar to the insertionIndex
of the factory with the difference that the validity of the index is only temporary.

When inserting two element that share a new vertex this vertex was inserted twice
resulting in a disconnected grid. The check if a vertex is already inserted was
already in place, however the map had the wrong scope and the pointer written
in the map was a pointer to the grid entity not the entity in the to-be-inserted queue.

Feature/remove entitypointer

* Remove EntityPointer from grid traits
* Remove deprecated entityPointer method following upstream changes

See merge request !13

[bugfix] You cannot dereference an entity

This fixes the broken setposition test.

See merge request !11