Create GUI interface for all g-cal settings options

[FFJohnN]

There should be an easy interface for users to select their settings for the google calendar integration plugin beyond one that is triggered with the command /gcal settings. This work should explore creating a generic interface that can be used to change all settings in the google calendar integration plugin. This interface should easily allow for the addition of new settings and their relevant selections.

A/C:

• Create modal for plugin settings
• Add one category of settings within the modal or create dummy settings for this POC