-Readability/consistency improvements for Pushbullet.cs;
-Update FileUpload code in Pushbullet.cs to work with v2 of the PB API;
---Add new serialization objects for file upload request responses;
---Add more null checks since null responses may be more likely now;
-Remove unnecessary response data from old deserialization objects;
If you do not want Pushbullet URL copied to your clipboard then create a
new Hotkey e.g. Ctrl+Shift+P for Pushbullet and deselect Copy URL to
Clipboard in After Upload Tasks