Filters

Added general filter capabilities.

Stuff that could be better:
1) Code is kind of factorized, but globally in the same file (main.js), which should not be the case, but my coding was terrible, sorry about that. All suggestions regarding that matter are welcome.
2) Requesting routes from google every time user clicks on filter, which can lead to OVER_QUERY_LIMIT response if user's APM flies off the roof. Maybe add some kind of memory capability is the newly sent request has already been calculated ?? This may not be top priority because the main fonction of the app normally only requires one click (users that will click fanatically on the filters are just messing around).
3) No update position capability through GUI
4) Current filtering ergonomy:
- by default, all modes are active
- if all modes are active, click activates desired mode
- if not all modes are active, click activates/deactivates desired mode
- if no mode is activate, automatically activates all modes
Maybe add double click to 'activate only one mode' ??
5) Once optimized, this app should be a cross-platform standalone app. Need to check that out.