Improved error reporting location, and minor bugfixes.

Major changes:

• Better email address validation.
• Better validation for the references field:
  • post-dated references,
  • self-referencing references.
• Better validation for the resource field:
  • invalid mimeTypes,
  • non-base64 encoded derefUris.
• Better validation for empty feeds.
• Extended support for validation messages of different levels (i.e., severities).
• Code clean-up with introduction of Guava libraries.
• Extended test-coverage.

Major changes:

• support for XML signature validation,
• beta EDXL-DE support,
• added a profile for CAP-AU,
• added a profile for Google Public Alerts,
• incremental parsing in CapXmlParser,
• cap.proto refactoring to adhere to proto style guidelines,
• testing data refactoring,
• a few bug fixes.