Adding dataset dropdown to visualization (WIP)

* adding new sample to include dataset dropdown
* dropdown uses view from scoreboard.theme to fetch
  datasets
* adding new DatasetSelectFilter based on SelectFilter
* some jshint cleanup
dimension_options_xy requests now include dataset
jshint fixes
Adding category_facet dropdown
Updating tests
removed __dataset from annotations in sample
simplified samples (removed js code not used anymore)
datapoints still works for multi-lines chart if dataset facet not configured
Fixed embedding for multiple datasets
preserve parameters from url
removed indicator-group from filters
IE fixes, fixing tests components tests
Updating scenarios to fetch dataset cube
Merge branch 'devel-dataset-compare' of https://github.com/eaudeweb/scoreboard.visualization into devel-dataset-compare

Conflicts:
	scoreboard/visualization/jsapp/scenario/scenario.js
Set default value for dataset
Merge branch 'editor-fixes' into devel-dataset-compare
Adding dataset checkbox on edit form

* fixing some jshint warnings
* removing commented code
* adding new *multiple_datasets* property on model
* removing code that added "(X)"/"(Y)" to facet labels
* adding dataset facets when *multiple_datasets* is *true*
* moving *constraints* and *position* code to separate functions
* setting no constraints for *all-values* facets
Listing definitions only once

For multiple series visualizations, the definitions (annotations) are
now listed only once and get saved properly for all series
Merge branch 'devel-dataset-compare' into devel
fixed constraints on all-values (when multiple_series)