[Vc] Work around missing std::for_each_n() in g++ 7.2.

Closes #88

See merge request !341

`Vc/common/algorithm.hh` uses `std::for_each_n()` when it detects C++17, but
g++ 7.2 does not seem to provide it (yet).  Work around this by disabling the
macro that signals C++17-support in Vc.

Closes: #88.

Deal with Vc access proxies

Closes #59

See merge request !338

This is needed by the `luDecomposition()` in densematrix.hh

This is needed because newer versions of Vc introduce their own proxies as the
result of expression like `v[0]`.  These proxies cannot be constructed outside
of Vc, not even by copying or moving, so we cannot pass them out of our
`lane()` function.  We work around this by introducing our own proxy class,
that we can copy.

That proxy class was originally introduced for !193 (Proper SIMD Interface)
and has been backported for the 2.6 Dune release.

Closes: #59

bump version to 2.7-git [ci skip]

See merge request core/dune-common!337

parallel index sets: correct typo; return value of AllSet::contains() [ci skip]

See merge request core/dune-common!335

Fix module name for dunecontrol update

Closes #78

See merge request core/dune-common!332

Fix status message

See merge request core/dune-common!331

When dunecontrol update fails the module name no longer has
underscores instead of hyphens.

This fixes #78

We are not 'running' the doxygen documentation,
we are building it.

Replace throw by terminate in destructor

See merge request core/dune-common!327

re-enable transformTuple test fails with debian 8 gcc

See merge request core/dune-common!273

added a range function for range based for loops over consecutive integers

See merge request core/dune-common!325

[std] add fallback implementation for std::conjunction / std::disjunction

See merge request core/dune-common!322

Disbable a deprecation warning in a test

See merge request core/dune-common!328

Since the destructor is no longer noexcept(false) it
will never throw an exception to its caller but always
call std::terminate().

In C++11 destructors are implcity `noexcept` such
that a `throw` leads to a call of `std::terminate()`
anyway. Hence this commit does not change the behaviour
but only avoids a warning.

BTW: Destructors are `noexcept` for good reason, because
it is in general very hard to recover from a failing destructor.
This also applies here.

Require GCC 5 and C++14

See merge request core/dune-common!320

Feature/require cmake 3.1

See merge request core/dune-common!323

[bugfix] Correctly display headercheck status message

Closes #86

See merge request !326

Surprisingly, the -D and -P arguments to cmake are required in a specific order:
D before P!

implement optional similarly to the one propoed in C++14 draft N3690

See merge request !276

[cleanup] fix some typos

See merge request !321

This fixes warning:  extra ‘;’ with -Wpedantic in GCC.