Add general error handler

Added general error handler:

Added new attribute 'error_log_chat' to the Bob-database table. Now single chat reference can be added to be the error log for the bot
Changed default value of 'broadcast_enabled' attribute from Chat entity to be false
Now all errors uncaught in any update handler are caught by the general error handler. Error handler: 1) Logs the error 2) Sends message to the error log chat if defined. Error message contains contents of the update which handling caused the error and the stacktrace of the error that was not handled by the update handler 3) Notifies user in the chat from where the error was caused that there was an error which has been sent to the maintainers
Removed duplicate emoji unicodes from unicode_emoji list
Now if user tries to press button from chat activity that is no longer stored in memory (for example after bot reboot), the message is edited to contain notification that the activity has been time outed and the user should start new action with a new command. In addition the inline keyboard form the message is removed

M4R774 / bobweb2