Add caps lock indicator

[mikedizhur]

Is your feature request related to a problem? Please describe.
When caps lock is on, the icon is the same as shift. You don't know whether it's on shift or caps.

Describe the solution you'd like
Change the icon when it's on caps. Since it's an arrow pointing up with a line under it, shift could be just the arrow and caps the symbol that is used now.

[eliottmusk]

At least in Holo theme the color change when shift is active, you can choose the color, here I use white to disabled and blue for enabled state. But is important add a feedback when you lock the shift when you hold the key 1 second, currently don't has any feedback, so you don't known exactly the time the key locked, should add a optional vibration.