Standardize and expand entity management

[bmcclure]

This PR includes the following main changes:

• Entity type definitions can now include more metadata which informs Launchpad how to customize the user experience
• Added additional theme icons
• Created a generic Manage Entities window that is used by default unless overridden
• Allow opening a manager window for entities generically
• Expand CacheState to store response codes for cache items
• Build entity manager links in the Tools menu dynamically
• Add UrlObj class for advanced URL operations, and make HttpReq objects support it in addition to strings
• Bug fixes