New PE Body: Union

See merge request !4

WALBERLA_CHECK_FLOAT_EQUAL_EPSILON
WALBERLA_CHECK_FLOAT_UNEQUAL_EPSILON
WALBERLA_ASSERT_FLOAT_EQUAL_EPSILON
WALBERLA_ASSERT_FLOAT_UNEQUAL_EPSILON

Change Box to Capsule in rigidbody communication header

See merge request !13

getMaximumPenetration()
getNumberOfContacts()
getNumberOfContactsTreated()

two versions available now via CMake switch:
   - by default the Python module is built without LBM module, since
     lbmpy can be used for this. Reduces compile time substantially.
   - if the LBM is needed in python, for example for the lbmpy testsuite
     it can be included by setting the CMake switch
     WALBERLA_BUILD_WITH_PYTHON_LBM

- Bug occurred if a BufferSystem (or communication scheme) was copied
  and the first object went out of scope.
- Internally a pointer was kept which was still pointing to the original
  BufferSystem

Fixes #16

Merge branch '17-does-not-compile-error-cannot-convert-walberla-real_t-aka-double-to-real_t-aka-float' into 'master'

Resolve "Does not compile: error: cannot convert ‘walberla::real_t* {aka double*}’ to ‘real_t* {aka float*}’"

Closes #17

See merge request !9

Enhanced lbm::PerformanceLogger

See merge request !8

Various updates to ExprTk

See merge request !7

- can now use the current time step of an ITimeloop object as reference
- can now export data to SQLite databases
- added option to refresh cell counters on each call

Added compile-time check for vector indexing when using constant values

bugfixes and extensions for free_surface support

See merge request !3

Minor updates to ExprTk

See merge request !5

Updated multi-sub expression operator to return final sub-expression type.
Updates to exprtk_disable_return_statement macro for disabling return statements and associated exceptions at the source code level.
Various other updates

Delete CTestConfig.cmake

See merge request !2

If you have access to the old closed source waLBerla repository, you may restore the complete history with the following command
git fetch git@i10git.cs.fau.de:software/walberla.git 'refs/replace/*:refs/replace/*'