Changed the key code upgrader to only replace codes that appear in
"bindings" properties. Modifier flags such as MOD_LCTL are no longer
valid as key codes, but they are still used in "mods" properties and
should not be replaced there.
Moved the keymap upgrader to a top-level page like the power profiler
to make it more discoverable. It upgrades more things than key codes
now, so putting it in the codes category doesn't make much sense.
Converted the upgrader code to TypeScript and split it up into smaller
files to make it easier to add new upgrade functions.
Added upgrade functions to remove/replace "label" properties and rename
matrix-transform.h to matrix_transform.h.
