simcav/simcav: Mace

New release with standalone applications for GNU/Linux, Windows and Mac.

A few improvements:

New beam size plotting.
Fixed bug in stability plot modifying the actual resonator.
Made both saggital and tangential components positive (sharing axis).
Added optical elements labels in plot.
Added online version check to notify user of new version available (manual download tho!).
Possible to click status bar on updates message to go to SimCav website.
Checkbuttons now skip tab focus, for continuous tabbing through optical elements' entries.
Alternative background color for results window rows (odd/even). Improves readability.
Improve functionality: Move 'Delete button' to 'Elementbox'.
Relocate stability controls.
Redid manual.