Refs #1679 : Initial changes for VizMapper UI redesign--default values editor, vizmap editor and bypass all merged in the same visual properties sheet ("Visual Styles" panel).

Change-Id: I19458d294aa52cc189e7b5d3edb1d24585ffdbbd
Refs #1679 : Fixed issue with no default value icons when the session has no network views.

Change-Id: Icb9dee8f3dc7f383e22889bd3eb9d44ea8faaf1a
Refs #1679: Added visual mapping toggle button and removed the arrow icon. Added a header with labels to make it easier to identify the default/mapping/bypass buttons. The VizMapper now displays only the default visual properties when Cytoscape starts up.

Change-Id: I41d5a8ed27d36ad3a425cb50e95d339463fc3eaf
Refs #1679 : Fixed: table rows not updated correctly when switching from Continuous to Discrete Mapping; current visual style changed in an infinite loop after creating a new network view. Other minor UI improvements.
Refs #1679: Improved VizMapper look on Linux. The bypass button looks better when disabled, and don't show drop-down menu when the only possible action is to set a value.
Refs #1679: Adds bypass actions to network view context menu. Improves VizMapper buttons. Adds the expand/collapse buttons back to visual property sheet items.
Refs #1679: Adds context menu item for removing visual mappings. Deletes classes that created the old bypass context menu.
Refs #1679: Fixed removing visual mappings and editing discrete mapping values.
Transferred the responsibility of applying a modified Visual Style from VisualMappingManagerImpl to NetworkViewManager.
Refs #1953: Context menu items that generate discrete values are now disabled when the operations are not possible.
Refs #1969: Refactored vizmapper context menu.
Refs #1969: Added EditSelectedCellAction to context menu. Fixed scrolling with mouse wheel when mouse over a Property Sheet Table. Property values for Column Name and Mapping Type don't change when the new value is invalid (e.g. trying to set "Continuous Mapping" to a "name" column).
Refs #1969: Adds buttons for expanding/collapsing all mapping panels and for removing each visual mapping separately.
Refs #1969: Fixed the property sheet item's width when the scroll bar becomes visible, so the expand/collapse arrow is not hidden.
Merge branch 'feature/new-vizmap-ui' into develop
Refs #1969: Fixed selecting VizMapper's current visual style after current network view changes.