rename conversation.[ch] to purpleconversation.[ch] and split PurpleConversationUiOps out to its own file to avoid circular include issues.

Testing Done:
Compiled and ran locally including docs and pot file. The pot file fails as I need to rebase on [596](https://reviews.imfreedom.org/r/596/)

Reviewed at https://reviews.imfreedom.org/r/597/