fix - stealth tank, artillery

Someone changed stealth tank and it did not have HoldFire as initial stance anymore.
Apparently Explodes: does not use UnitExplode by default anymore? Fixed.
blue tree now 1/2 green tree's regrowth speed

Blue tiberium tree was producing at 58% of green tiberium tree.
It seems a bit too good right now, so going to put it at 50%. (It has ~2x value of green)
reduced cooldown time for ConYard to 5 secs.

8 seconds cooldown time for conyard seems unnecessary and a bit long. Reduced to 5 seconds. The build radius on its own will probably deal with most basewalking problems, so the cooldown time isn't as important. 
Increased Turret and Guard Tower's cloak detection range to 5. They need the range, especially since they are relatively easily destroyed by stealth tanks. 
obelisk range +1

Seems like Obelisk is not used much and that it is underpowered. Could use +1 range.
Rationale: it uses tons of energy (150) and costs a lot ($1500), compared to ATWR (30 energy, $1000) which has a range of 8. (Obelisk is 7 at the moment).
Obelisk also is comparatively easily destroyed since its HP are lower. Since it's vulnerable to power outages and artillery, it seems a bit more range will help get better use out of it.
Merge pull request #2925 from psydev/patch-2

fix - stealth tank, artillery; minor changes