Make use of favico an option

@tribut: does this resolve your issue?
Update title with unread count

Further discussion required on a few points:
* show notifications only or unread lines as well?
* only use this when favico is disabled, or indepently?
I welcome all feedback.

Fixes #22
Only update title for notifications, not other kinds of activity

Also make the unread count the first thing in the title
localstorage: Correctly check whether value is set before setting default

The old condition always overwrote boolean values that were set to false
with the default m( Check for undefined instead.
Merge pull request #163 from lorenzhs/flashtitle

Flash title when receiving lines in the background & make use of favico configurable