Default time period configurable on the WMS layer with a time dimension

[pomadchin]

GT Server should provide configuration settings to define the default time period that will be proposed in the GetCapabilities document of the WMS service. It should be possible to specify the type of default time period by specifying the oldest time, the newest time or any arbitrary time period based on ISO 8601:2000 (summarized in Annex D of the WMS specification).