override `remove` function to fix #1140
removed copy/paste of canHandleAdd function
#1151 - Allow partial order discounts

(cherry picked from commit 24206f5465fdde2480c23cc05e972ea6ae033f62)
#1137 - Fix z-index issue with admin date picker
#1137 - Fix z-index issue with admin date picker

(cherry picked from commit 71ca2857b670e5010840f68e8f8ff94e2bef4a97)
Merge branch 'BroadleafCommerce-3.0.x' into BroadleafCommerce-3.1.x
Merge branch 'BroadleafCommerce-3.1.x' into develop