Refactor ircbot

[misaakidis]

• Move hello messages to a separate file
• Clean up regular expressions and move them to a separate file (same with the hello messages?)
• Reply to messages that don't match the existing regular expressions with a help message
• Support for multiple IRC channels
• Follow the coding style of the rest of the codebase

@alexdor

[Drakevr]

add to that a more descriptive "update message"?

id est for now when an update happens the bot will say "Update on repository repo-name"
it would be far more useful to say "Update on repository repo-name (ref: $LINK)"

with link being either the commit title or the sha1 (better the commit title).