Improve keyboard steps

[metate]

Flashing the keyboard is necessary but interferes to user interaction. Reducing keyboard detection time does not help. Hiding the keyboard behind the selection dialog is not possible due to focus issues. A solution is important because writing players with keyboard steps is easier then looking at addon code or generated library strm files.

Possibilities:

1. Run keyboard tasks first (i.e. fill the tasks poll with all tasks that require keyboard but only run these just until the last keyboard step), then continue in normal execution order. This will make all flashing happen at startup instead of while the user interacts with the selection dialog. May be able to hide it behind a window with high zorder.
2. Increase task pool size (?)
3. Addon developers may not care to make the minor change that allows skipping keyboard steps (see flix2kodi). So just submit PR to make the change.
4. Skin developers may be able to hide the keyboard when Meta is running (if we set a property in the home window).
5. API for addon developers. We implement a template of function that recieves all Meta parameters of a media to play and create a directory with link(s) to display in Meta (or empty directory if media is not available). This function would have a standard endpoint and be discovered automatically by Meta so such addons would be available in Meta's 'Enable players' settings if the addon is installed without requiring a player. My only concern is that illegal addons will implement it, thus making the false impression that Meta is related or encourages use of these illegal addons.
6. Try intercepting the keyboard window and move its position out of screen.

[metate]

Current patch works on some skins (run numeric keyboard in the background which makes most skins hide the regular keyboard)

[metate]

In master it should work on any skin (Edit: but detection delay isn't high enough?)