Use new downloader methods, falling back to static if required.

Change-Id: I5330ef3fe6d9d6893a933d6639a2cd586ffddbfa
Depends-On: I5200f8d84e409cb71c5f7338bca18af6de4c0726
Depends-On: I38151f7c99de90b06e9a29c81e351361d9c6f75b
Reviewed-on: http://gerrit.dmdirc.com/3601
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>