* Add support for global verbs
These are verbs that are visible for all entities, regardless of their components. This works by adding a new class `GlobalVerb` and a new attribute `GlobalVerbAttribute`. It works in the same way as current verbs, except you can put the verbs class definition anywhere instead of inside a component. Also moved VerbUtility into it's own file since it now has functions for both verbs and global verbs.
* Add view variables verb as an example of global verbs
* Implement suggested changes
Implemented some suggested changes from code review:
- Remove unneeded attribute from `GlobalVerb`
- Added some useful attributes to `GlobalVerbAttribute`
- Moved constants used by both `Verb` and `GlobalVerb` into `VerbUtility`
* Reduce duplicate code in VerbSystem (client & server)
Greatly reduced the amount of duplicate code for handling component verbs and global verbs separately.
* Update engine submodule
Need this so client side permissions checks are available.
