enable multi language analsysis

Signed-off-by: Jorge Costa <jorge.costa@tekla.com>
Small refactoring: inline CxxPlugin:isEnabled()
Fix file ending.

Files got commited to Git with CRLF (windows) file ending, causing issues on
linux.
Merge pull request #141 from Typz/crlf

Files got commited to Git with CRLF (windows) file ending, causing issues on
linux.
Force inclusion of a header file for all checked/parsed files. This is an option most static code analyzer support.

- support one ore more header files (comma separated list): sonar.cxx.force_includes=header1.h [,header2.h]
- force include results in #include <...> (system header file)
- files are included in the order of definition (from left to right)
- search path from sonar.cxx.include_directories=...
Merge branch 'enhancement/force-include' of https://github.com/guwirth/sonar-cxx into enhancement/force-include