FEATURE: Low Tuning Bass Fix featuer in DLC Packer/Unpacker Tab

# contributors/thanks
myself, and some great help from @L0FKA. And thanks to the metal.

# description
Rocksmith 2014 has trouble detecting bass tuning below C1. Due to this, many songs cannot be played bass wise in correct tuning. However, a workaround has been devised (see here: http://customsforge.com/topic/5227-5-strings-bass-and-low-note-recognition/, credit to firekorn) in which we set the pitch to 220hz, and raise the tuning of each string by a full 12 steps (full octave).

# features
1. Automates the entire, tedious process of applying the low tuning bass fix to just a few clicks. 
2. Quick Fix option that saves working folder/files in the source package's directory, and appends the newly fixed files with '_bassfix'.
3. Delete Source Package option which deletes the original source package after creating the fixed file.