Create toggle to always draw crosshair

[acelad88]

Description
With the possibility of players using external crosshairs (whether via software/hardware), it gives these players an unfair advantage in two ways:

• When sniping, the crosshair persists and shows the true bullet destination (as the default scope is slightly offset, which is a legacy bug in itself)
• When leaning, the crosshair persists

Solution
A variable to allow players to toggle whether crosshair is always drawn e.g. cg_alwaysDrawCrosshair 0/1.
If set to 1, this should result in the crosshair showing at all times, including the two aforementioned situations.

Alternatives considered
The alternative that other modern games may take is banning external crosshair programs via anti-cheat software, but even if that was technically feasible it would be my preference to even the playing field through a positive (enhancement) rather than negative (limiting).