Fix issue #132 : Fix performance window timeings for graphs that don't generate EC_PAUSED and don't contain a time measure filter.
As a backup, set the start of playback time when play command is issued.
For graphs that also generate EC_PAUSED this start time will be overwritten by the time the EC_PAUSED event is received.

git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@196 c2f33eb2-41b2-391d-4cb4-d9d0608729ba