Version a map when publishing

[ScottEvil]

As a user I need to be able to publish a map so that the GeoGit layers are set to a specific date/time (commit) in order to keep the map in the state it was when particular decisions were made.

Acceptance criteria

• When the map is published it sets the view for the GeoGit layers to the commits for that particular time
• When anyone goes to that "versioned" map, it displays the commits for the time specified when the map was published
• The GeoGit repository continues to update as people add information
• In new or non-versioned maps, the default is the most current commit
• The date/time of when the map was versioned is displayed prominently on the display
• The map metadata says that the map is versioned to a specific date/time
• The map view has a note that reminds users that non-GeoGit layers are not versioned and therefore may have updated info since publish time.