The context menu is a standard way to expose operations of the clicked
item to the user. They expect it to be there, and we can make use of it
as a place to put more advanced operations in.
The menu contains:
* New Catalog
* Delete Catalog
* Rename
Also removes the 'x' icon to delete a catalog from the right side of a
row. This was just placed there temporarily until the context menu is
there. It's too easy to accidentally delete catalogs with this.
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