[keyboard layout applet] Make keyboard layout label vertically centered

After this change country code written in lower case will be vertically centered on panel.

If country code contains 1 or more uppercase characters - lineHeight will be set to 1.0 (default).

Keyboard layout widget before change:

After change:

It would be nice if someone test this change on a HiDPI monitor.

PS:
it was reverted because of problems on HiDPI display and others.
Alternative approach is here: !502 (closed)