[Feature] Keep track of server state to greatly improve usability of extension

[andrerom]

Today it's left to the user to keep track of if server is running or not with not visual clue on this besides errors if you click wrong icon / menu choices. If extension would somehow keep track of server state, this would make it possible to improve usability of the extensions on several fronts.

Improvements possible if extensions kept track of server state:

• Like suggested in Add visual indicator about server status #94: Be able to have visual indicator of state on icon in file action buttons (currently blue icon), could be white when not running like other icons, and blue when running or red like toggle file blame Git icon
• When clicking to open file extension could start server if needed, reducing need to have both a "Serve Project" and a "Open file in browser" menu choices, menu choice + icon on top bar would both open file in browser, but first start server if needed
• Menu choices for Reload and Stop server could be greyed out when not running