* Changed Python scripts so they work on my machine

file open() used default encoding (cp1252 on my machine) but the text is utf-8, had to specify encoding in check_layout.py

This can spot mispelled special keys.

Change the format of check_layout.output to avoid adding any logs for
layouts that do not trigger any warning.

Fix the check_layout CI, which was broken since check_layout.py was
changed to take arguments.

The attribute 'c' specifies the symbol in the center of a key, just like
'key0'. This adds consistency with the cardinal direction attributes and
is intended to make layouts more readable.

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.