Moved several hard-coded UI strings to strings.xml

I noticed some strings were not localised when my phone was set to French, and then realised that these strings were actually hard-coded. So I moved them all to strings.xml, which also required some minor code changes to get the context in scope, in order to fetch the string in some cases.
Right, I'll fix the indent.

The variable was already there, I just moved it outside of the "try" block to get it in scope. But I feel it makes the code more easy to read than referencing ConversationActivity.this everywhere), so I think it's fine to leave it like this.