make buildtest output coloured
Merge pull request #474 from OlegHahm/buildtest_coloroutput

make buildtest output coloured
mute build tools (to be consistent with the rest of the build system)
build everything in the project directory
move include directives from header to C file
simplify and unify include pathes

additional:
* exporting include path in sys is mandatory for subfolders
* removed duplicate object file in linker call
correct filename
simplify include structure for boards

* do not overwrite CFLAGS in boards Makefile
simplified and unified cpu build structure
removed redundant include pathes from Makefiles
removed superfluous slash after BINDIR
further Makefile cleanup
use proper variables in board Makefiles
create BOARDS subdirectory for binaries
muting compiler and binutils optionally

Instead of muting all compiler and other binutils output by default,
introduce a variable to make this behaviour configurable.
add basic include pathes by default
fixed typo
moved muting "logic" away from application Makefile
added missing mute prefixes in nativenet and shell
fixed include path for mbed board