Let FindTrilinos to set HAVE_TPLXXX

I still need to lifeconfig.h, but it is easy ;)

Changed the type of some cached CMake variables.

Removed from CMakeLists.txt (unused) checks for some standard C
headers. Also removed the corresponding defines from lifeconfig.h

Added CMake find script. Library is optional, must be specified
when it has been activated as a Trilinos dependency

Bug found in the detection of QHULL in non-standard location
Adding hooks to search for SuperLU and SuperLUDist

Set the LIFE_BUILD_DOCS variable to "TRUE" during configuration
to be able to build the LifeV PDF documents.
There are still bugs in the document creation procedure and the
doxygen API documentation is still not created.

This variable is now exposed in the CMake GUIs (default TRUE)

Default values are set now for C++ compiler, build typexi. TPL
flags are by default set to FALSE and can be changed from ccmake.
This should make it easier to use a graphical frontend of CMake.

These files make it possible to configure and build LifeV with
CMake