Add Tooltips to all Context Menus

[CryZe]

This adds tooltips to all context menus. In particular, there are now tooltips available that describe the functionality of each component.

[CryZe]

@wooferzfg Would be great if you could check the descriptions again for any wording issues and stuff. Also as you can see in the screenshot I tried some new grouping with the timer components being grouped and the key value components also being in their own group. Not sure if it's a good idea.

[CryZe]

Also ideally this entire context menu in the layout editor should just be entirely in livesplit-core, with all the tooltips and groupings probably being in there instead. But that can come in some later refactoring. The refactoring would probably also allow hovering the components that are already in the layout, for the same tooltips.

[wooferzfg]

The grouping you came up with seems good.

[CryZe]

Thanks for reviewing :)