Add button to count watcher and debug mode

Performance issues are mainly caused by spurious angularjs watchers.
This debug mode provides a button to display the number of registered
watchers in the console.
Add bindonce and remove 50% of the watchers in the buffers
Improve feedback
try to improve scrolling experience
Remove autofocus since it is very mobile unfriendly
Consume less space on mobile
Improve mobile layout

* more densely packed channel switching buttons (increased their size to better match android design guidelines)
* disable zooming
* disable scrolling to the side