Fix not interrupting downloads in Firefox

Fix minimum file size to interrupt

- Adopted by uGet team as our official add-on
- uget-chrome-wrapper has been renamed to uget-integrator.

Please remove uget-chrome-wrapper and install uget-integrator.
For more details: https://github.com/ugetdm/uget-integrator/wiki/Installation

Support for downloading from YouTube*
To download, right click on Youtube page and select uGet Integration -> Download video with uGet

YouTube Note: uGet respects the YouTube Policies so depending on the individual settings of a video it may not be possible to download video from YouTube. The vast majority of videos will be available for use in uGet.

- Allow -1 file size
- Fix duplicate URLs in batch download
- Store extension properties in storage.sync

- Added `Download all links with uGet` option to context menu
- Fixed Firefox loading the file after interruption as a text file
- Fixed interrupting small files
- Fixed picking default download location of Firefox as filename