Moved DeployOrderTargeter.cs from OpenRA.Mods.RA to Common

First step in moving all the not-mod-specific code from project OpenRA.Mods.RA to OpenRA.Mods.Common.
Pretty much a test commit. Includes only 1 file moved and "using" statements added to the 7 files that use it.
This breaks our convention that those should be ordered alphabetically.