MoreCast: Refactor weather parameter tab state into an array

We're running into a race condition when toggling the visibility of weather parameter tabs and the Forecast Summary tab. To reproduce:
1. Launch MoreCast and click the RH tab so both temp and rh are visible.
2. Click the Forecast Summary tab
3. Click the RH tab.

Actual Result: Temp and RH are both visible
Expected Result: Only the RH tab should be visible.

I believe this is happening due to each tab having independent state for managing its visibility and that we can workaround the problem by using a single object to manage the state of all the tabs.

Start by locating the MoreCast weather parameter tabs and Forecast Summary tab state, then reproduce the three-step sequence described in the issue. Trace how visibility is updated when switching tabs. Done means selecting RH after Forecast Summary leaves only RH visible, with the existing behavior covered by an appropriate test if the project has one.

Written by the indexing model from the issue text.