* Incremental work on custom activities
* Incremental work on refactoring versioned entities
* Add ActivityDefinition infrastructure
* Incremental work on activity definition manager
* Incremental work on API endpoints
* Refactored flowchart component to include hierarchical nav
* Incremental work on modularization of designer component
* Restructuring into modules
* Rename CustomActivities module
* Apply security
* Fix activity definition GET endpoint
* Incremental work on activity definition provider
* Incremental work on activity definition execution
* Update ActivityDefinitionMaterializer.cs
* Update ActivityDefinitionActivityProvider.cs
* Add activity definition referenced version update handler
* Maintain position of not found activity
* Fix prefix naming
