Converts 'constraints' to local variable in order to fix desktop sharing issues(audio constraints were retained in global var and get desktop stream failed).

Adds jicofo install instructions.

Prevent XSS injection using 'nick' tag on presence

Fixes chat messages

Adds 'jicofo' package to Deinstall section.

Fixes configuring prosody which can break also jicofo configuration, the missing domain will fail later creating admin account for jicofo.

Fixes a smile typo that causing missing image

Does not reload the page when "focus left MUC" event is generated after we have left the MUC intentionally.