Add Alt-Tab Switcher Delay

[Isaac Parris]

Relevant -
https://bugs.launchpad.net/gala/+bug/1154696
https://bugs.launchpad.net/gala/+bug/1220718

The current window switcher behavior can be disorientating; I often run a dual-monitor setup and want to quickly switch between two windows that I'm typing in and the windows will twitch if you switch them too quickly. I also find that it's easier to just use the slower meta-W then the window switcher because you might have to cycle through the windows once or twice before getting to the window you actually want.

I propose this change:

Adding a slight delay after pressing alt-tab, so that the user can quickly switch between two open windows (text editor and document for example), and the windows will continue to their normal fade function once held down for long enough, allowing the user to cycle through the windows and find the one they want.

I can code this and have been working on it for awhile. Any input is appreciated.

With the Isis plugin support, it might be an option for the user to choose how the window switcher functions also; how much delay, etc.