Add import of tags, radius and links to CSV importer

[stefanhahmann]

This Pull request adds some extensions to the current CSV importer.

It adds 3 additional features that can be imported using it

• A tagset and taggings belonging to it
• A "parent_id" so that Links between spots can be imported
• A radius so that a radius column could be used which would be preferred over the fixed radius that can be specified for all spots

In order to maintain usability, while the dialog is growing two new sections are introduced:

• Mandatory
• Optional

The PR also contains some technical (hopefully) improvements:

• Open CSVReader in try-with-statement to make use of the AutoCloseable
• Let CSVImporter extend ModelImporter so that listeners are paused during import
• Add .trim() to remove leading and trailing whitespace before number parsing. Without this I encountered some problems in a test dataset
• Add class to StartImageJ with Mastodon Pasteur Plugins included (for development process only)

The dialog would look like this if this PR is accepted:

Unit tests:

• The PR contains a unit test for the newly added features

[stefanhahmann]

Resolves #15