XNAT-4387 Made auth methods fully customizable via plugins. If none are specified, it will default to db authentication, but if any are specified, only the specified ones will show up. I also added support for an order property to control the order of the methods in the dropdown, as well as the order in which they are checked when users attempt authentication. I see this plugin-based way of configuring providers remaining as an alternative to AdminUI configuration once that is implemented.

XNAT-2429 XNAT-4201 XNAT-4423 Massive refactoring of libraries to get rid of split into root and application contexts. Moved lots of initialization from autowired fields to autowired constructors. Added method to create DICOM SCP instances without specifying ID since ID is now generated and provided. Fixed broken login on su operations.

Converted security to mostly use Java config to allow injection of preferences during initialization. Fixed scheduler issues.

Added support for initializing site URL from request URL and servlet context. Finished StringUtils migration. Added XapiRestController handling.

integrate gradle-xnat-plugin and work out configuration for Cargo deploy
tasks.