Add corporation role filter and other improvements

• Adds corporation role filter
• Add "character type" property to skill set filter [1]
• Adds tests for asset filter
• Improves page load of asset filter form
• Improves performance of asset and compliance filters (plus refactoring)
• Renames app so it is sorted next to "Secure groups" on the admin page (since those two are used together)
• Simplify pyproject.toml by switching to flit

Open

• Rename related name "role" to "roles" in Member Audit (bug)
• Add "main only" to filter

[1]: This allows creating auto groups for something like fax alts