VIB-lib: Segmentation editor/ CustomStackWindow.java: Speed improvement

Improved ROI application speed for cases when there are no locked
materials.
Merge branch 'master' into optimize_segm_editor
VIB.segment.CustomStackWindow: Improved speed for both adding to and
removing from material.
Merge pull request #14 from quazgar/optimize_segm_editor

Optimized segmentation editor further