Unhardcode integer key IDs

[sprunk]

These shouldn't use string.byte or raw numbers. Use Spring.GetKeyCode instead, or perhaps KEYSYMS (KEYSYMS is sort of deprecated too but commonly used and acceptable for now). 304 is probably just left shift, test if right shift works. Part of the task is to look around if there's more of these.

Zero-K/LuaUI/Widgets/gui_attackrange_gl4.lua

Lines 846 to 852 in d050274

	if key == 304 then
	shifted = true
	end
	if key == 46 and mods.alt then
	CycleUnitDisplay(1) -- cycle forward
	end
	if key == 44 and mods.alt then

Zero-K/LuaUI/Widgets/dbg_ballisticcalculator.lua

Lines 375 to 385 in d050274

	local incCylinder = string.byte( "/" )
	local decCylinder = string.byte( "." )
	local targetingMod = string.byte( "\\" )
	local hideBallisticPlot = string.byte( "n" )
	function widget:KeyPress(key, mods, isRepeat)
	if ( key == incGravity ) then
	customMyGravity = customMyGravity + ((isRepeat and 1) or 0.1)
	return true
	elseif ( key == decGravity ) then