Add option to bump the ProductVersion for RC/DPROJ targets

[darianmiller]

Open question - should it sync with FileVersion or bump independently.

Leaning towards independently with -VersionKey ProductVersion capability which defaults to FileVersion if not provided, but could be overriden to bump just ProductVersion.
Also add -VersionKey Both to keep them both in sync.

Perhaps:

{
  "file": "...",
  "target": "RC",
  "style": "WinVer",
  "part": "build",
  "versionKey": "Sync",
  "fileVersion": { "old": "1.2.3.4", "new": "1.2.3.5" },
  "productVersion": { "old": "1.2.0.0", "new": "1.2.3.5" }
}