Created conversation class with base read/send

Created a conversation class to more properly encapsulate conversation
behavior. Right now it just covers sending/reading messages.
Fixing conversation/one-time pad

Modifying the functions so that they work properly together.
Code cleanup

Removed some old/unused code and cleaned up some comments.
Code cleanup
Fixing emulator crash on message load

It was crashing due to failing to load any messages. Restructuring the
loop hopefully will fix this without breaking anything else.
Rearranging code

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Refactored conversation details

- Moved most of what was in Conversation to MessageHandler
- Moved reading text messages to Conversation
- Added a consistent Conversation reference to Hub
Shifted sending into Conversation

Moved a skeleton function into Conversation that encryption can be
slotted into once it's ready.
Comments and skeleton functions