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.