Have "Save" and "Restore" buttons in both the tool preset list/grid
and the tool preset editor. The save button stores the active tool's
options in the preset, if possible.
In order to make things more obvious here. Before, a tool preset could
only be rstored from the list by selecting it, which only worked if
another preset was active before. Now the selected preset can easily
be restored again.
and remove them from the various public construct() functions. Had to
change construction in GimpDataFactoryView slightly because of GObject
construct property constraints.
