Improve support for MSVC

See merge request !249

* Use standard file permissions
* Use pi from dune-common

Simplify domain creation

See merge request !248

This clarifies the ownership.

And note that in the long run, the method should be removed completely.

There is no need for that.  Simply passing them around by pointer
is much easier.

Previously, it was a static method and the BVP_Descriptor object
held a pointer to that method.  In the old days, this was
used to make the Configure method, well, configurable.

Now we just expose the method in std_domain.h and
let the UGGrid implementation in dune-grid call the method
directly.

Fix more MAX_SONS regressions

See merge request !247

It wasn't used anymore.

Fix segfaults created by recently lowered value of MAX_SONS

Closes #62

See merge request !245

Simplify setup of GENERAL_ELEMENT prototypes

See merge request !243

Quantities like the maximum number of corners per side where
previously set to the 3d value, which is much too large in 2d.
Give the correct values depending on the dimension.

The split is historical, and serves no purpose anymore.

Instead of in a method.  That's more direct and readable.

The old implementation was over-engineered: An edge always
has exactly 2 corners.

They were merely copies of the code & documentation in gm.h.

It was never actually used.

... which explains why it could be set to '0' for prisms and pyramids
without causing any bad effects.

Designated initalizers are easier to read, and they allow the compiler
to catch more bugs.

Update to 2.11

See merge request !244

Add max buffer size to printf functions

See merge request !241

Unbounded buffers triggers warnings in Apple clang

Write a README.md file

See merge request !240

To help people understand what this module is about.

Mark various pointers const

See merge request !239

Found by Cppcheck (constVariablePointer)

Fixes Cppcheck warnings constVariablePointer

Found by clang-tidy (readability-non-const-parameter)

Found by Cppcheck (constParameterPointer).

Improve refine.cc

See merge request !238