Add Policy Editor Warnings for Empty or Unintentional Fields

### Problem description
Currently when creating a Policy when a user mis-configured something the policy engine will display an error in the dry-run mode. However there are many situations where something is not an error, but can be considered unusual (such as an empty field) and thus is likely to be unintentional. Policy authors need some way of quickly identifying such issues which would hopefully help them to debug policies quicker. Similar to how most compilers display both ERRORS and WARNINGS.

### Requirements

- Create an extendable list of situations/configurations of blocks etc in Policies which can be considered 'suspicious' - such as empty 'important' fields', strange values in variables, etc
- Introduce a new 'WARNING' type of messages printed out by Guardian in dry-run mode which can be switched on/off by the policy author
- Introduce a UI workflow where a policy author would be quickly navigated to the 'offending' place/setting by clicking on the warning

### Definition of done

- Functionality is implemented as described above
- Appropriate level of documentation is created to cover the new functionality
- An initial list of 'suspicious' configurations is built into the Guardian so users can benefit from the functionality from the first release

### Acceptance criteria
UX for policy authors is improved by allowing them to switch 'verbose' mode of dry-run in which WARNINGS are displayed in addition to the usual ERRORS