WebTV: Attempt at providing touchscreen-compatible navigation

I take no responsibility if this commit boils your kittens, runs off with your wife, or - more likely - doesn't work on the preferred esoteric browser of your choice. If you insist on running Netscape on CP/M then that's your problem.

This is a quick-and-dirty attempt at adding some touchscreen-compatible controls to the HTML TV player. This is done purely so we can more easily test transcoding on tablets and 'phones.

Specifically, this PR:

1. Adds paging buttons so you can move through the list of a gazillion channels we all have,

2. Makes that list scrollable without a keyboard (arrow keys otherwise), and

3. Adds a 'Play' button so you can launch a channel without the evidently-missing 'Enter' key

It will inevitably not render properly on all platforms - I've tested it on Firefox on Ubuntu only - but that's a task for another lifetime...