Dev enable time interval search

Hello

this pull request contains an improved handling of the time filter:
* enable time Interval search, TimeIntervall filter will be activated when the search query contains a pattern like this ```YYYY-YYYY``` p.e. ```1976-1980```
* the time filter can be a year (passed by get Parameter time timeInstant or a year range
* the time filter attribute in sphinx is called ```year````
* the filter is only activated when the layer index contains the year attribute
* mixed feature searches are now possible (timeEnabled and normal Layers/Indices)