Introduce first version of widgets on maps.
Mockup available here.

Please indicate if this issue is related to a bug or a new feature request

• Bug
• New Feature

Acceptance Criteria - AC

• You can (optionally) configure and add widgets to the map by selecting a layer and clicking on the widgets button in the TOC. To allow widget creation WPS gs:aggregate and WFS must be available. Otherwise a message should inform the user that widgets are not available.
• You can specify a filter to apply to the data before aggregate
• You must specify chart type, and then X or Y axis attribute (in case of line and bar chart) or group by and value (pie and gauge chart), operation to aggregate. Then you can select color (or color range) of the chart.
• You can enable the chart to "sync" with the map. This will filter the data behind the chart on the current viewport. This filter is applied together with the specified filter.
• You can choose to display/Hide legend
• You can insert title and description for the widget and add the widget to the map
• You can save the map with the current widgets
• You can edit existing widgets on the map or export data (as image or csv file)
• You can see the tabular version of the data in the chart from the widget UI