switch editor should allow !swx

[michkrom]

all across GUI the switch editors should allow !SWx so a new specialized func (gui_edit_swich) should be introduced.

[art103]

I had done this with + / - ints previously:
gui_int_edit(g_eeGeneral.trainer.mix[i-1].swtch, inc, -NUM_SWITCHES, NUM_SWITCHES);

I guess I need to take a git pull and get up to speed with the latest code.