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=...

Conflicts:
	sonar-cxx-plugin/src/main/java/org/sonar/plugins/cxx/CxxPlugin.java
	sonar-cxx-plugin/src/main/java/org/sonar/plugins/cxx/squid/CxxSquidSensor.java
* Add switch (setHighPrio) to MapChain to add macros LowPrio or HighPrio.
* Replace putHighPrio and putLowPrio with put. put uses one or other list depending on setHighPrio=true/false.
* Add macros inside of handleIncludeLine with 'macros.putHighPrio' (indirect by setting setHighPrio=true).
* Add second source file to test project.
fix path issue: use / instead of \
Merge pull request #139 from guwirth/enhancement/force-include

enhancement/force-include