Add min range to bazookas

Fixes #7000
Move the core of OpenRA.Mods.RA.Scripting to OpenRA.Mods.Common.Scripting
Lazily generate buffer in Sheet.

The managed byte buffer is created on demand, meaning a newly allocated sheet will not waste memory holding onto the buffer until some changes are actually required to be written. This avoids a newly allocated sheet wasting memory on buffers that do not differ from their backing texture.
Made Sheet.Texture into Sheet.GetTexture() since we will want to call it for side-effects.

Do the same for Sheet.Data since it has the side effect of generating a buffer.
Release sheet buffers in SequenceProvider and MapCache.

The buffers in SequenceProvider can be freed if Preload is called, since we know everything is loaded. A SequenceProvider is created for each TileSet is use so this saves memory for however many tilesets had been used in the game. This will be at least one for the shellmap, and often more.

The MapCache loading thread is kept alive for 5 seconds after it last generated a map (in anticipation of more requests). Once this time expires the thread is allowed to die, as it is unlikely there will be more requests in the short term. At this time it is ideal to force the changes to be committed to the texture so we can release the buffer. As well as marking the buffer for release, we must access the texture to force the changes stored in the buffer to be written to the texture, after which the buffer can be reclaimed.

Additionally, when starting the MapCache loading thread we must ensure the buffer is created from the main thread since it may query the texture object which has thread affinity. After that the buffer may be modified freely on the loading thread until released.
Use more locking to improve thread-safety in Sheet.
Merge pull request #7009 from obrakmann/fix7000_e3_close_range_fix

Add min range to bazookas
Merge pull request #6756 from RoosterDragon/release-more-buffers

Release more sheet buffers
Merge pull request #7013 from atlimit8/ModsCommonScripting

Move the core of OpenRA.Mods.RA.Scripting to OpenRA.Mods.Common.Scripting
Second implementation of Sandworms

Fix tabs in AttackSwallow.cs
Step three in implementing sandworms

Removed/fixed comments
Code style fixes

Fixed AttackWander, addressed style nits

Fix Travis crash
Improved visuals, added WormSign norification
Add RadarPing on worm spawn, fix wandering issue, add new Wormspawner.shp
AttackWander style fixes
bring back the thumper

merge medic and engineer into a new support infantry

Fix Travis crash