Structural updates based on best practices and feedback
Structural updates based on best practices and feedback

# Renamed the compression property to jpegCompression to be more
consistent. also set default value to default system value
# moved constructor to the reset() method which is automatically
invoked by Loader::helper
# returned $this on setJpegCompression method to allow for chaining
(e.g.
Loader::helper('image')->setJpegCompression(20)->getThumbnail($file,200,
 100);
# modified min level to be 0 per imageJPEG method's acceptable range

Former-commit-id: 26ef84d6b123cdf210d86ad5354e89b5fce2872a
jaromirdalecky/concrete5,concrete5/concrete5,rikzuiderlicht/concrete5,triplei/concrete5-8,biplobice/concrete5,biplobice/concrete5,acliss19xx/concrete5,jaromirdalecky/concrete5,triplei/concrete5-8,deek87/concrete5,biplobice/concrete5,haeflimi/concrete5,deek87/concrete5,hissy/concrete5,mlocati/concrete5,olsgreen/concrete5,jaromirdalecky/concrete5,a3020/concrete5,haeflimi/concrete5,mainio/concrete5,mainio/concrete5,a3020/concrete5,hissy/concrete5,MrKarlDilkington/concrete5,KorvinSzanto/concrete5,deek87/concrete5,rikzuiderlicht/concrete5,haeflimi/concrete5,deek87/concrete5,KorvinSzanto/concrete5,mlocati/concrete5,haeflimi/concrete5,mainio/concrete5,mlocati/concrete5,biplobice/concrete5,concrete5/concrete5,hissy/concrete5,olsgreen/concrete5,mlocati/concrete5,olsgreen/concrete5,jaromirdalecky/concrete5,MrKarlDilkington/concrete5,concrete5/concrete5,acliss19xx/concrete5,triplei/concrete5-8,concrete5/concrete5,hissy/concrete5,acliss19xx/concrete5,MrKarlDilkington/concrete5,KorvinSzanto/concrete5,rikzuiderlicht/concrete5