Allow for multiple checkbox and list/item pairs in parameters.

Allow for multiple checkbox and list/item pairs in parameters.

List/item pairs should now use the following syntax:

    list=name item=value   -->   listitem=name:value

Isolate code to handle deprecated parameters (checkboxon, checkboxoff,
list, item, mastery) into OvaleAST:FlattenParameters() so that other
modules no longer need logic to handle the deprecated features when using
parameters.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@1551 d5049fe3-3747-40f7-a4b5-f36d6801af5f