Add topoJson support

[Flaminietta]

Changes to export data in topoJson format from any kind of input data.

ING-3131

[Flaminietta]

Done

• modified the UI
• the jar file of a modified version of the project https://github.com/bouviervj/topojson-j is imported into our package (locally for now)

Problems

• some TODOS to solve
• how to go from InstanceCollection to FeatureCollection, or other solution
• writing the topology on a string (and not on a file)

[Flaminietta]

My blocker is that I don't know how to add instances into a FeatureCollection object. When this is solved, then I can use the FeatureCollection directly in one method of the new library to create the topology.

[Flaminietta]

The new plan is to first write the instances into a shape file and then convert the shape file into a topoJson.

BLOCKER: in TopoJSONInstanceWriter at lines 105-106 by debugging I see that it never enters the try-and-catch block. The instances are probably never written into the shape file. And line 86 is skipped, therefore no conversion shp-->topoJson happens. I cannot find why.

[florianesser]

@Flaminietta I'll close this in favour of #991