Added cleaning *.pyo in case Python Optimization is enabled.
Added few toFormat() tests.

Some fixes are also included.
FrameTime interface redesign.

* Changed initialization method of FrameTime. A correct way now is e.g.: FrameTime(25, time=15).
  It's described in FrameTime ctor doc-comment.
* Removed string operations from FrameTime.__set_time__()
* Fixed some problems with (still) incorrect float arithmetic.
* Added several public getters. They are now used in several places instead of direct attribute
  access.
* A lot of new FrameTime tests written. Some others were split into smaller testcases to improve
  their clarity.