Reduce Stealth damage vs. infantry 35% -> 25%

Playtesting has shown that the Stealth Tank is a little bit too good against infantry, which are supposed to be its (soft) natural counter. They are the only units which can detect the stealth tanks, so it's important that they not die too easily. Right now it seems that stealth tanks are able to sit and fight infantry very easily, especially since they outrange them. This change will discourage stealth tanks from engaging infantry without care.
Reduce RangeLimit of Stealth Tank Missiles

Note: the "Range" value of the Stealth Tank remains the same. 

It has been noticed that the missiles of the stealth tank seem to go on for forever (~11.5 cells), making them inescapable; their range is 7, so this is a large difference. Their range limit is being reduced so they will travel only 8.3 cells now.
Nerf Mobile SAM damage a bit

The Mobile SAM has been shown to be exceptionally powerful in small groups, being able to annihilate large groups of helis. While the cost could be increased, it seems like a few changes for now would be good and mitigate some of the OPness.

Changes:
-Replace quick-firing 2-burst and replace it with 1 shot per second.
-Reduce damage to 32. This will make it kill Apaches in 4 shots instead of 3.
-Reduce missile speed from 426 to 341. (This will also effectively reduce range limit from 12.5 cells to 10).
Reduce BikeRockets' speed a bit

Bike spam is quite effective, and seems almost too good at silencing opposition. After playtesting, it was found that reducing the speed of rockets gives whoever they are engaging a chance to fire back before dying.
(RangeLimit increased to compensate for speed change, to keep it above 6).
Merge pull request #6010 from psydev/patch-3

Minor balance tweaks for TD