Modified Makefile to create a easy to link shard library for e-Paper display
driver for Raspberry Pi (C code).
This way, it is more easy to link against this code when creating custom
projects which use that e-paper screen.
* Reorganized src variables
* Created 2 new targets: make lib and make example (and make all)
* make clean now does not file if files do not exist
* make clean removes bin directory. There is a target which create it
automatically
