Exclude *.c files from make doc
Introduce macro to define files that should be deleted on make clean
Move .elf file to it's own target
Make directory creation in object compilation more makey
Merge pull request #1137 from authmillenon/no_c_doc

doc: Exclude *.c files from make doc
Merge pull request #1098 from authmillenon/make-addon

make: Make make more flexible