Allow duplicate colors when map has LUA script

[Flamefire]

For e.g. campaigns the creator might intend duplicate colors so allow that.
This also resolves the issue where color set by LUA is changed as it is
still taken even though the conflicting players color might get changed
right afterwards so colors would be unique when the script is done.
That makes setting the colors dependent on the order which is hard.

This also makes the behavior consistent with the documentation.

Fixes #1884

[Spikeone]

@Flamefire I just had a look at the docu (probably for that one the first time):

SetColor(color or colorIdx)
Sets the players color by index or directly if its alpha value is not zero. Duplicate color values are possible, so you have to ensure unique colors if you want them!

So we can add any color? And can we maybe document the colorIdxs (guess there is an array somewhere). Also what does happen if we use an invalid index (guess just nothing)

[Flamefire]

So we can add any color? And can we maybe document the colorIdxs (guess there is an array somewhere). Also what does happen if we use an invalid index (guess just nothing)

Yes any color. I enhanced the documentation to refer to the array and stated that custom colors are ARGB.
An invalid index will cause the function to fail/abort. I didn't document this as it is clear this is an error and we don't document such things in similar places, e.g. for GetPlayer(idx)

[Flamefire]

@Flow86 *ping