This adds the clipboard pane, which allows to save an arbitrary number of
clipboards and to paste them later. The key can be disabled in settings.
Checking the "Recently copied text" checkbox will cause the keyboard to keep a
temporary history of copied text. This history can only contain 3 elements
which expire after 5 minutes.
If this is unchecked, no history is collected.
History entries can be pinned into the persisted list of pins.
Incompatible APIs were used in the custom layouts and the extra keys
options.
Add @TargetApi annotations to help catch similar issues in the future
with the help of 'gradle lint'.
This separates the layout definitions from the special layouts
(bottom_row, greekmath) and other unrelated files (method, settings).
This is also a more intuitive location for layouts and make the resource
directory easier to navigate.
Under the hood, layouts are copied back into
build/generated-resources/xml.
