Refactor Style and Condition arguments

Closes #38

Significant refactoring of conditional and static styling capabilities:
- Conditions and styling should now be specified in a JSON-like string format, like {backgroundColor:#009900,color:#33ff33}. The legacy comma-separated format is still supported in the Matrix telemetry CSV file, but the new approach MUST be used in the Matrix Layout file.
- Static styling can now be defined in the telemetry file.
- Border style can now be specified, like {border:1px solid #ff0000}.
Condition Widgets can now be created without a telemetry reference, and can now include URL properties to make them function as buttons.
Hyperlinks are now created simply with _link; urls must be specified with a separate _url() property, which can also be applied to Condition Widgets.
'Output messaging' enhanced to use grid layout and provide additional detail.
Added Stacked Plot creation back into prl-to-display. Plots are now collected into a Tabs view, similar to Display Layouts.
Enhanced TabsView creation to allow setting of the "keep_alive / eager load" property.
Help page has major updates.

charlesh88 / openmct-scripting