Chatbox opacity setting and scaled down width for

lower resolutions than 1920x1080.

Also fixed sliders not scaling their handle when resized down/up from
the default.
Hybrid MotD mode

Shows text on connect, but opens the webpage when the player uses the
vote menu or the chat command to view the MotD.
Slightly better scaling at lower resolutions

Still needs more work, but it shouldn't take up the entire screen on low
resolutions now.
Fixes #258

The MotD window was not calling SGUI:EnableMouse( false ) when it was
told to open again while already open which caused the mouse window
count to increase each time.
The chatbox now acceptably scales down

At resolutions at or below 1280 width, the chatbox uses a smaller font.

Also fixed SGUI messing up after a resolution change, and fixed text
entries having their first character slightly cut off.
Merge pull request #259 from Person8880/develop

Chatbox fixes