Added system_icon/system_item deprecation
Added system_item/system_icon deprecation error.
Added more deprecations (more)

- Removed DBT directives (not needed)
- Renamed a couple test files
- Cleaned up PM::Styling a bit
- Removed some unnecessary alias methods
Merge pull request #468 from clearsightstudio/refactor/deprecation_warnings

Refactor/deprecation warnings