Improve validation/linting

[joachimmetz]

Improve validation/linting to:

• detect multi line documentation string that does not have long docs with a white line after the first line. Also see Style Guide
• detect duplicate paths
  • Registry keys
  • Registry values
  • etc.
• non existent artifact names defines in meta artifacts
• check for WOW64 missing Registry key aliases
• detect cyclic artifact groups
• check naming
  • artifact definitions in windows.yaml should always start with Windows
• detect duplicate sources section?

sources:
sources:
- type: FILE