Async key generation

[arlolra]

• [x] Add the ability generate keys asynchronously in a worker
• [x] Use the async worker to generate keys on account create, or as needed
• [ ] If we somehow get to starting an OTR session w/o a key, grey out the conv browser with a message and throbber, and generate the key synchronously, rather than launching a modal

[azadi]

I think this is a great idea, especially since we are enforcing private conversations by default, which means that all accounts will need to generate keys at one point or the other. On account create would be great.

[vqhuy]

@arlolra : I am trying to resolve the task 3 but I am struggling to get the uiConv. I think I need to modify the method ui.generate but I cannot find any way to get the uiConv to grey out the conv browser. Do you have any idea?

[arlolra]

create_privkey_cb is called with only an accountname and protocol, which makes sense, given that it is going to generate a key to be used for all conversations with that pair. We probably need a utility like getUIConvForRecipient that returns all the matching conversations to be greyed out. Does that help?

[vqhuy]

yup, I got it. Thanks!