some fixes related to mesh editing

[vcloarec]

This PR fixes some minor issues related to mesh editing:

• fix cancel/rollback, the triangular mesh was not properly updated
• fix layer extent after editing, the extent was not updated after adding/removing some elements
• fix vertical extent after editing, the min/max of vertices Z value, was not properly updated
• fix 3D update, the 3D view was not updated if the editing was cancel or rollback
• fix dataset group name update, there was an issue with the displayed text of elevation dataset group.
• fix mesh transform coordinate dock widget, there was a bad handling of this widget.
• send the reindex action to the mesh menu instead of a button in the tool bar