Fixes compilation with SuperLU 7 by forcing backwards compatibility

See merge request !591

SuperLU 7.0.0 now uses singlecomplex instead of complex and by default
does not add a typedef to make singlecomplex available as type
complex. The latter was used in previous versions.

As we need to support several versions of SuperLU we force adding such
a typedef by defining SUPERLU_TYPEDEF_COMPLEX

Replace pthread_exit(NULL) calls by return NULL

Closes #121

See merge request !589

Get rid off unused-variable-warnings.

See merge request !579

Fix constructors in iterators

See merge request !584

Update set_package_properties for ARPack and SuperLU

See merge request !585

Improve support with MSVC

See merge request !577

* Handle float exception handling for MSVC
* Remove system specific includes
* Make iterator in block vector be copyable to fulfill output iterator interface

simplify and cleanup the SolverFactory

See merge request !453

getMatOrThrow handed out a reference to the underlying matrix, but for
the compiler it was undecidable, whether this might be a dangling
refernce. This lead to many warnings. We now hand out the
AssebledLinearOperator and call getmat explicitly where ever needed.

In the rewrite the vector types of UMPack were checked, similar to the
other direct solvers. This does not work anymore, as recent changes in
UMFPack now lead to a compiler error if the vectors are not available,
i.e. when using a real-type different from double. This change now
(re-)introduces a SFINAE check to ensure that the types are compatible.

cleanup a range of warnings

See merge request !583

Catch polymorphic type ISTLError by reference

See merge request !581

Found by GCC (Wcatch-value)

Update changelog release 2 10

See merge request !576

Update versions release 2 10

See merge request !575