Refactored JS code and added line creation call

1) Created API object that contains all direct communication with the PL
server, including debug calls. The API object is accesible by its global
pointer. To call an API function simply run javascript:API.<func>

Example: javascript:API.debug_uri_options("http://localhost:5000/circle");
2) Refactored all server interaction to go through the API object
3) Renamed qr_objects.js to webqr.js, to better capture the content
4) Added POST call to create a line object