Moving Android on screen keyboard button from SDL to ManaPlus.

Also add basic functions for handling other on screen buttons.
Added /atkhuman command
DidYouKnow and Help windows customized xmls added.
Jewelry Theme update. New window background graphic, general bug-fixes.
More text contrast in Help window added.
More contrast between enabled/disabled button.
Add Keyboard button in Jewelry Theme for Android.
Extend on screen keyboard button.

New theme options:
    x - x position
    y - y position
    padding - button padding
For android change option "custom cursor" to "show cursor"
Fix input tab size in settings.
Add support for on screen joystick for moving.
Improve screen joystick handling.
Enable OpenGL by default under Android.
Hide unsupported OpenGL renderers under Android.
Disable beings popups under Android by default.
Add padding properties to Keyboard icon in Jewelry Theme.
Add theming to browserbox.

New theme file: browserbox.xml
New theme options:
    padding - padding for browserbox
    newLinePadding - additional padding for new line wrapping.
Save drop shortcuts after clean operation.
Add a bit constexpr.
Add support for persistent directory under Android.

This directory used for updates, configs, logs.