Add semi-randomized player faces

[ETLegacyTeam]

Author: @rmarquis (Spyhawk)
Date: 2019-04-18
Redmine Issue: 1253, https://dev.etlegacy.com/issues/1253

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ET has 5 classes in each team, each having an uniform clearly designed to be easily recognizable during battle.
It would however be great to introduce more cosmetic variation, with semi-randomized faces for each player. If not random, they could be selected from a bigger pool of available faces.

See "ET-HQ":https://github.com/acqu/wet-headquarters from acqu. which implements a complete character customization system - though I doubt we should go to that extreme.

If you've ever dreamed of playing as a medic while proudly harboring a mustache, this is for you!

[yfcz]

AI generated faces like this would be really cool. :) https://thispersondoesnotexist.com/