Confirmation for logging out

* New confirmation function
* Made interface functions accessible through window.Interface
Optimize logout confirmation

Re-use window instead of creating a new one each time
Fix Dwarf Fortress launching on Linux.

The launching is still not without problems (the standard streams get muddled
with dfterm3 standard streams) but the Dwarf Fortress does not freeze.

This commit also consolidates Windows and Linux launching to the same module.
Remove useless admin.html. It was not being used at all.
Merge branch 'ui' of git://github.com/lethosor/dfterm3
Fix unintuitive command line option behaviour. (GitHub issue #2)
Don't hardcode WebSocket ports.

Until now, the port 8000 was hard-coded to playing.html (the playing interface)
as the WebSocket port. Now, the command line options are taken into account and
passed on to the client browser so that it knows which ports it should really
connect into.

If more than one port is specified, a port is selected at random.
Fix hlint warnings.

Just one this time.
Add some feedback when a game is being launched to the interface.

Previously, if the Dwarf Fortress was not running, the interface would not give
any kind of feedback that the Dwarf Fortress screen is (hopefully) going to
appear in a few seconds. Now we show a small "starting up..." text to let the
user know at least something is happening.
Tell the players if the game is gone in the web interface.

Before, there was no indication the game had crashed/shut down other than the
screen not moving. Now you get a wonderful red and bright message.
Handle keypresses in more detail.

This makes shift+arrows work. And this commit requires dfhack plugin update.
Fix Windows build.
Update README.md