Add Makefile magic to exclude specified modules

Allow modules in tools and utils to be completely eliminated from the build.

Add the partial path of the module to eliminate to src/makefile in the EXCLUDE_MODULES variable
for instance tools/touchprobe utils/panel

In main.cpp modules that can be removed need to be bracketed with a define like so...

#ifndef NO_TOOLS_TOUCHPROBE
     kernel->add_module( new Touchprobe() );
#endif

The define is automatically created by the makefile system as shown.