revising landingPage language 

In response to https://github.com/project-open-data/project-open-data.github.io/issues/370
adding expanded guidance for license 

In response to https://github.com/project-open-data/project-open-data.github.io/issues/196
adding reference to license
2 small style changes
first pass at metadata v 1.1 mapping

Changes that still need to be addressed are changes in structure and should we add usage notes additions here or no?:

* Adds optional describedByType field at the dataset and distribution level (#291, #332)
* Changes contactPoint field to an object that contains the name (fn) and email address (hasEmail) (#358)
* Adds fn field as part of contactPoint replacing earlier use of contactPoint (#358)
* Changes publisher field to an object that allows multiple levels of organizations (#296)
* Changes accessURL field to represent indirect access and to exist only within distribution (#217, #335) 
* Changes format field to a human readable description and to exist only within distribution (#272, #293)
* Adds optional description field for use within distribution (#248)
* Adds optional title field for use within distribution (#248)
* Changes accrualPeriodicity field to use ISO 8601 date syntax (#292)
* Changes distribution field to become required-if-applicable and to always contain the accessURL or downloadURL fields (#217)
* Changes license field to be a URL (#196)
Merge remote-tracking branch 'upstream/metadata-v-2.1' into gh-pages