Attributes for VOMS/GridSite

Added to the configuration file, but commented out.
Minor dep updates
Added forgotten option to config docs
Clean-up in authN strategies

* Removed old ToDos
* Cleaner logging
Updated docs in authentication strategies
Partial updates should result in 501

* Not Implemented (waiting for OCCI 1.2)
Impl. trigger_action_on_all for DummyBackend
Impl. basic trigger_action for DummyBackend
Updated default auth. strategy order

"basic x509 voms" => "voms x509 basic"
Fixed parentheses (code formatting)
Refactored VOMS strategy (=> YamlHelper)
Added ACLs and name mapping to KeystoneStrategy
Fixed docs in SpecHelper::Warden
Fixed docs for AuthenticationStrategies::Helpers
Fixed YamlHelper (static context)
Added specs for DummyStrategy and spec helpers
Cleaned-up and extended DummyStrategy specs
README simplified

Since all the relevant content was moved to the GitHub wiki, this README is now much shorter.
Merge pull request #4 from sustr4/install_defaults

Install defaults II
Moved DummyStrategy specs to their proper place