Use Bluemp's UploadHandler class

Signed-off-by: Suki <suki@missallsunday.com>
Some text strings and some other stuff to make it work

Signed-off-by: Suki <suki@missallsunday.com>
Handle storing the file name on breeze_options
Create a static property for coversFolder name
Modify the JS to only allow one upload at the time and add a cancel button
Add some more language strings

Signed-off-by: Suki <suki@missallsunday.com>