correction of type identifier (send_grid_t and local_grid_t) in some functions.
introduction of timing estimates identified by an enumeration.
implementation of first fft estimate.
introduction of timing estimates identified by an enumeration.
implementation of first fft estimate.
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