Add new module OvaleScripts to manage scripts from multiple sources.

Add new module OvaleScripts to manage scripts from multiple sources.

Move the existing default scripts into OvaleScripts and decorate them with
a description that allows a user to see what class specializations are
supported by the default script.

Teach Ovale to use the script ``source'' to find the code for the current
script.  Custom code can be copied from an existing script to a blank
custom template that may be modified and saved into the SavedVariables
file.  The script ``source'' may be selected from a dropdown menu, with
the default menu containing the Ovale default script and either a blank
custom script or the custom script loaded from the SavedVariables file.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@715 d5049fe3-3747-40f7-a4b5-f36d6801af5f