TEIIDDES-2340: Modify Change button in Model Explorer view to be icon

* Fixing the dimensions of the button squashes the text if default font
  size is larger then dimensions allow

* Flat button contains too much grey border which makes the button look
  clunky on the section toolbar

* Using an icon allows for a fixed set of dimensions and using an image
  hyperlink removes the grey border
TEIIDDES-2340: Fixes lack of widths in TableViewers

* Provides a TableViewerBuilder class to encapsulate the creation of a
  TableViewer in its own composite, which then sets its layout to
  TableColumnLayout

* Columns are created using the builder and their weights set appropriately
  ensuring that each column has a minimum width

* Not all viewer columns have been converted due to specific requirements
  for each one. For example, table viewers in a form section seem to
  throw SWT errors.