The scheduler now has its own Scheduler::GetPhaseFrameBudget() function

and uses it for the old two: Scheduler::GetInterphaseBudget() and Scheduler::PrintPhaseBudgets().
The latter two functions used to rely on Cell::GetPhaseFrameBudget() in order to
do their job. This had two drawbacks: There had to be at least one cell in the scheduler,
and the reports of the two functions were biased by the used cell's randomized cell cycle length.

M    src/cell.h		- just added a comment in the Cell::GetPhaseFrameBudget()
M    src/scheduler.h		- clarifications in the docs of the budget functions
M    src/scheduler.cpp	- the two old budget functions now rely on the new one
								- added the new one: Scheduler::GetPhaseFrameBudget()
M    src/main.cpp		- decent clean up in the simulation branch of the code