GUI, feature, and performance updates

GUI:

• Moved various controls to Settings menu
• Added Mode and Action toolbars
• Added additional View toolbar buttons
• Added menus with help and info links
• Set reasonable step values for window and level based on loaded data intensity range
• Added interface with segmentation controls
• Added split region interface for splitting into > 2 regions
• Added loaded image and segmentation file name labels
• Added check if attempting to save segmentation data as current image filename and vice versa
• Set autorescale as default
• Disable most GUI controls/menus until data loaded
• Add buttons for X, Y, Z, and resetting view

Features:

• Added clean region
• Added 2D floodfill

Performance:

• Improved segmentation performance
• Improved loading segmentation data performance
• Improved region splitting performance for images with > 8 bits
• Improve paint/erase performance by waiting until mouse button release to update region table
• Use single click/drag/release for undo/redo when painting/erasing instead of each individual voxel change
• Check for change in z before rescaling window/level

Platforms:

• Added Linux build

Bug fixes:

• Fixed TIFF saving issues
• Fixed issue with updating progress when no .json file
• Fixed bugs with setting region done and text color when loading metadata