Add FindSplash.cmake

- add components support for PARALLEL
- add version support

Note: HDF5 tends to add *some* mpi libs already. but the same
problem as with bullxmpi happens if one does not link the _cxx
part, too. So we decide to add them anyway to be sure.
Add FindSplash to png2gas Tool
Tools: png2gas/splash2txt use new Cmake Module
Move splash2txt to src/tools
Move Dir with Modules down to src/
Add Install Routines for splash2txt
Update Install Instructions for Tools
Use less error-prune static lib option

the manipulation should affect as less other stuff as possible,
e.g. double linking a shared and a static mpi library will fail
in most of the cases with weird errors