0tu when a soldier revives via Heal.

 - was already done for revive via Stimulant (copy code up)
Grenade activation warning messages.

 - shows red warning when activating grenades in Tactical. But...
   only works for Proxies in the preBattle equip screen (someone
   with more understanding of thinkers & timers might do it for the
   other grenades, on preTactical screen)

- 2 line change ( intended to replicate behavior of original )
Closes the inventory screen on RMB

 - only if *not* in preBattle screen! otherwise things get weird...
Remove path preview when using action menu or inventory

Fixes
- bug 253.
- using a medikit or psi-amp with a path previewed leaves that
inaccurate path on screen.
- accessing inventory with a path previewed leaves that potentially
inaccurate path on screen.
Update path preview when unit kneels
Add missing setup for tank only missions
Avoid code duplication
Merge pull request #637 from cfailde/tankonly

Add missing setup for tank only missions
Merge pull request #634 from cfailde/bug253

Remove path preview when using action menu or inventory
Merge pull request #633 from kevL/inv_exit_rmb

Closes the inventory screen on RMB
Merge pull request #631 from kevL/heal_revive_fix

0tu when a soldier revives via Heal.
Merge pull request #632 from kevL/gren_act_warn1

Grenade activation warning messages.
Flat rate for weapon shots.
UI cleanup
Woo sliders!
Merge remote-tracking branch 'upstream/master' into myk_fix_warnings