update to .NET 4.0
Migrate to System.Lazy.
Reduce hijacker hp from 80 to 50
Merge pull request #5082 from pchote/dotnetfour

Upgrade to .NET 4.0
Increase ra husk hp from 140 to 280 and increase burn damage
decide which mirror to choose locally and display result

closes #3904
Merge pull request #5086 from ScottNZ/balance

More RA balance tweaks
clean up after MonoDevelop/Visual Studio
Update INSTALL

* .NET 4.0 #5082
* SDL 2 #3315
* avoid trademarks
Update INSTALL

we now require a .NET 4.0 compatible compiler
Minor explosion weapon sound fixes
Adds Explode weapons for ships and submarines
Adds visible explosions to ships and submarines
Adds Explosions to all vehicles that didn't have one.
fixed Dune 2000 powerdown cursor palette
don't play crumble sound when placing concrete
add the beacon button artwork to RA, D2k and TS

thanks to @xanax
Fix stupid typo, use UnitExplodeSubmarine for MSUB.
Fix typos in vehicles.yaml
Merge pull request #5091 from reaperrr/ra-vehicle-explosions

Add RA vehicle explosions
Fixes #5077