Refactored how app is init (tray creation, etc.)

- moved init stuff from index.html to init.html (which itself replaces
list.html)
- renamed index.js > init.js
- renamed index.html + script.js > add.html + add.js
- moved server-list.js from /server to /client
Implemented watchr (start and stop)
Clean tests & comments
Added a lock state to avoid multiple template uploads at once
Added auth (login:pwd) in server URLs. Blank for now.
Auto-close Add window after 2s, once it is submit
Removed useless comments
Display Add window always-on-top
Created an init method, and externalized tray menu creation for watched folders

So we can use it later to create tray menu for new watched folders.