Merged C-interace into single file
Create tests subdir.
Rintroduced constants to remove dependencies of ScaFaCoS-Code.
Makefile.am to build test programs.
First steps of splitting off P3M interface in subdir src/.
Merge remote-tracking branch 'gsichardt/p3m-refactor' into p3m-refactor

Conflicts:
	lib/p3m/init.cpp
	lib/p3m/src/prepare.cpp
	lib/p3m/src/run.cpp
	lib/p3m/src/timing.cpp
Details
Removed max_particles.
summation and collection of timings moved to function (usable by ik and ad).
ik FFT estimate fixed.