mako template for compile_commands.json

[rottaran]

http://clang.llvm.org/docs/JSONCompilationDatabase.html
A couple of code analysis tools use this. For example https://code.woboq.org/

[rottaran]

This does not work with the current design. All of our make rules refer to many variables from the header of the makefile. The compilation database template would need the content of these variables, not just their name. Hence, we would need to integrate real processing of variables and rules in mcconf instead of leaving this to make.

=> Depends on issue #25 and #26.

Consider https://github.com/nickdiego/compiledb as alternative to generate the compilation database from the makefile when needed.