Expand and diversify Crate Bonuses.

[SoScared]

The crate bonuses can often be experienced as underwhelming. With the current time delay the bonuses gathered with a crate seldom has any impact in the game. There's a few alternatives that could add some good fun with the crate option:

• Increase veterancy rank level-up bonus.
• Add firepower/armor/speed upgrade (as in the original) and add an appropriate visual tag to the upgraded unit.
• Increase bonus levels over time (cash, unit multiplier...).

[SoScared]

First step at https://github.com/RAunplugged/uRA/commit/2a454b88033d7fe228d695308b996ed5a7ca144f

[SoScared]

expanded and polished with multiple commits: https://github.com/RAunplugged/uRA/commit/e027fcdde59fbb0d7a2da98f8090a80e779b7425, https://github.com/RAunplugged/uRA/commit/d70f4fef520edc6de3935a9640d54923a5dc673a and https://github.com/RAunplugged/uRA/commit/66c393bba07f9b9a3c0849d1e81f638106d10ae7