Fix image memory use#2045

Merged

rhukster merged 2 commits intogetgrav:developfrom

tsnorri:fix-image-memory-use

Jun 8, 2018

Commits on May 31, 2018

Add a method for freeing the image file, free each derivative after it has been created
tsnorri
committed
Save the scaled derivative on disk before freeing it, store its path
tsnorri
committed