Fix the start time of an action displayed in the icon.

Fix the start time of an action displayed in the icon.

This had assumed that the current time was in the first interval of the
time-span, which is not always true.  Implement a new method for
OvaleTimeSpan to determine the next time given a starting point, and use
that method instead of making the assumption.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@1177 d5049fe3-3747-40f7-a4b5-f36d6801af5f