Set default preference ...

... for MUC notifications to true
Fixed some strange wording in a string

Still doesn't sound right to me though...
A few typo fixes in the README
Went a bit wild on the README...
Merge pull request #570 from SamWhited/typo-fixes

Minor typo fixes, and big changes to README
Merge pull request #569 from kriztan/patch-1

Set default preference ...
keep reference to previous and next message in message
refactored avatar generation. first step
proper avatar caching
update ui when new avatar was found
fixed #564
throw exception when no servers are left to try