Added ability to control SW/LR stereo mode with keys.

Ctrl + Up/Left/Right will set the active SW stereo mode.
Ctrl  + Alt + Up/Left/Right will set the active LR stereo mode.

Modes:
Up = Both
Left = Left
Right = Right
Updated English Readme with new key combinations.
Changed default stereo keys for LR from Ctrl + Alt + Arrow Keys to Alt + Arrow Keys
Added EN Readme credit for code changes.
Added key combination to cycle through available SW/LR radios.

Ctrl + Shift + A/D = Cycle through SW radios.
Alt + Shift + A/D = Cycle through LR radios.
Added radio cycle keys to EN Readme.
Update README_EN.md
Swapped condition checks to attempt to reduce used cycles.
Update fn_processLRStereoKeys.sqf
Update fn_processSWStereoKeys.sqf
Update fn_processLRStereoKeys.sqf
Update fn_processSWStereoKeys.sqf
fixed config error on rf7800str
forgot the idc's for last fix
fixes #434
Implemented lazy eval on logic for alive players & having a SW/LR radio.
Added stereo mode key combinations to stringtable.
Switched SW/LR array logic to use _forEachIndex var.
Switched SW/LR for loop to use exitWith to avoid unnecessary loop cycles.
Shorted logic for setting active radio & cleaned up private variables.