Fix and Refactor spinbutton toolitem
fixes #690 (closed) and #689 (closed)
image-updated till commit b3537605 13 is not a "standard" value but is 8+5(page) while 8-5=3 is a "standard" value hence is original value and its label is preserved and value uniqueness is maintained at all times.
UI
Page up/down feature exists for fast changes, removed duplicate and out of bounds values labels preserved
Development
Optimized API for densely as well as sparsely labeled data.
Edited by Abhay Raj Singh