Cycles-Bake: Move "Output File" section to the bottom of the bake panel.

The reason for this is heirarchy. During the order of operations the output file is likely one of the last
things you'll set. First the type and width, then margin, then specifc settings, and finally the output file.

Doing this also helps avoid breaking up the settings that are specific to baking, such as the Type and "Selected to Active".
Cycles-Bake: Renaming 'Custom-Cage' to 'Cage'

As suggested by Andy Davies (metallandy):

The Custom cage title is not correct. Custom cages are when the user has
modified the topology of the cage by moving verts/topology and meshes
under this slot do not need to have modified verts/topology in order to
work. They could use a regular mesh or have one imported from another
application so just calling it Cage mesh or Cage object would be
perfect. Calling it cage mesh goes against convention for all other 3d
applications so it's just going to cause confusion.