Improve Entity Selector

[Drachenkaetzchen]

The entity selector is very bare-bones and doesn't allow searching and filtering. Additionally, the user has to add fields manually.

1. Add searching and filtering
2. Define a default set of important fields to all PartKeepr entities and display the important fields in the entity selector
3. Implement a mechanism to generate canonical names from entities

For example, important fields on a part would be "Name", "Category" and "Storage Location". A canonical name for a part would consist of the part's name.

[Drachenkaetzchen]

Searching and Filtering must also be applied to the export view.