Enhanced the image helper to allow for instance-specific JPEG compression level
Enhanced the image helper to allow for instance-specific JPEG compression level

I felt there was a need for the image helper to occasionally render
very high quality JPEGs (my usage was a zoomable map), and there was no
functionality to do this on a per-image / -block basis. Should be a
fairly straight-forward upgrade.


Former-commit-id: 48d4cf14d1062c8f244389ef87c5eccb67f4fc6c
concrete5/concrete5,mainio/concrete5,olsgreen/concrete5,mlocati/concrete5,acliss19xx/concrete5,haeflimi/concrete5,jaromirdalecky/concrete5,hissy/concrete5,olsgreen/concrete5,triplei/concrete5-8,hissy/concrete5,rikzuiderlicht/concrete5,deek87/concrete5,concrete5/concrete5,mlocati/concrete5,biplobice/concrete5,deek87/concrete5,a3020/concrete5,MrKarlDilkington/concrete5,KorvinSzanto/concrete5,mlocati/concrete5,biplobice/concrete5,KorvinSzanto/concrete5,jaromirdalecky/concrete5,haeflimi/concrete5,haeflimi/concrete5,MrKarlDilkington/concrete5,olsgreen/concrete5,biplobice/concrete5,hissy/concrete5,acliss19xx/concrete5,deek87/concrete5,MrKarlDilkington/concrete5,KorvinSzanto/concrete5,deek87/concrete5,acliss19xx/concrete5,concrete5/concrete5,rikzuiderlicht/concrete5,triplei/concrete5-8,a3020/concrete5,hissy/concrete5,biplobice/concrete5,concrete5/concrete5,jaromirdalecky/concrete5,mlocati/concrete5,jaromirdalecky/concrete5,mainio/concrete5,triplei/concrete5-8,haeflimi/concrete5,rikzuiderlicht/concrete5,mainio/concrete5