Client Files: Set flag when files enqueued and don't process files unless in current context (header/footer)
Client files: Do not set hooks when no files registered
Merge branch 'opt-file-enqueue' into develop
Viewer: Optimize theme validation
Viewer: Remove redundant code in `reset()` method (use existing API method)

Closes #110
Merge branch 'iss-110' into develop
Base: Stop script enqueue hook from passing arguments to callback
Base: Validate arguments in `enqueue_client_files()`
Merge branch 'fix-file-loading' into develop
Controller: Optimize hook initialization (don't set public hooks for admin requests)
Controller: Set hooks *after* request has been fully parsed

* Resolves #111
Merge branch 'fix-is_enabled-init' into develop
Controller: Move client file declarations to `_client_files()` method (Basic)
Client Files: Pass directly from child to base `_client_files()` method
Admin: Refactor client file declarations
Client Files: Replace formatted/placeholder text with dynamic values in file declarations

* Context
* Dependencies
Merge branch 'rfr-client-files' into develop
Re-route all widgets through SLB (to handle widget activation)

* Update: Modify widget callbacks when SLB enabled (allows SLB to handle widget activation)
* Update: Check if widget is being processed in `SLB::process_links()`
* Update: Admin check added to `SLB::is_enabled()`
* Remove: Redundant `is_admin()` calls.

* Ref: Issue #125
Util: Update documentation
Add: Exclusion methods