Rename EthShield to ethshield
Move Makefile directory up
Structurizing Makefile
Rewritten Makefile

It now searches for sources to compile, so no manual adding new
files. It puts object files in to ./obj instead of aside of the
source file. And the executable and related files (elf, hex, lss)
are located in the build directory.

These directories are configurable in the Makefile.
Update .gitignore with directories for objects and build
Merge branch 'feature/makefile' into develop