Updates to menus, commands, new settings

**Bundles of fixes that includes updates to menus (Sidebar, Context, Main) for visibility and availability.**

* Fix for menu item availability based on file extension, update ```util.get_file_extension()``` to use native methods.

* Hide or disable sidebar items when not an MM project or not a metadata file as appropriate.

* Update order of some menu items and add ellipsis to menu items that open a new window

* Update to "Open On Server" and "Open WSDL On Server" to separate functionality between active/selected menu commands, and fix for "Refresh Selected Files" to use the proper command. 

* Check ```is_mm_project()``` based on active folders and not project file in case project file is outside the workspace. 

* New user setting ```mm_compile_rollback_on_error``` to allow setting rollback on error for compile project to false - currently returns errors as JSON, update to parse coming soon.