Updates to CUB's layouts

This update is mainly needed because Ergodox's layout should be as much
possible closer to original QWERTY layout, to not break XKB layout in
XOrg for Russian language.

Also, because Ergodox's switches SW5.7 and SW5.8 are not as convenient
as I'd like to - additional mappings were added on Layer7 for following
symbols: ^ ' " \