New base class for verification resource.

Refactoring to support multiple credential verifications.
Setup for multiple attributes
Also show some rudimentary info about verifications
Merge branch 'refactor' of github.com:credentials/irma_web_service into refactor
Also add ProtocolInfo
First refactoring steps
Refactor AID to variable
Preliminary inclusion of issue code
Add error-handling to resources
Spuiten en Slikken new style page
Massive rewrite for issuing

Now have nice demo-pages for mijnOverheid that do:
 1. Landing page with explanation
 2. Verification of an attribute (SSN)
 3. Landing page two, with list of credentials that can be issued
 4. Multi-issuance of credential in IRMA style
Use ProtocolCommands instead of List<ProtocolCommand>
Merge branch 'refactor' of github.com:credentials/irma_web_service into refactor
Show checking 'Attributes'
Show status of credentials while issuing
Removed unused function
Show verification errors
Issue error handling and minor improvements

Added error-handling for issue-ing. Tweaked the state system to stay
in a consistent state. Handling of server side errors remains to be done.
Merge branch 'refactor' of github.com:credentials/irma_web_service into refactor
Merge branch 'refactor' of github.com:credentials/irma_web_service into refactor