Replace 'Cubeviz' refs and add crude versioning.

Changed all refs to 'Cubeviz' into 'Thea', and labelled as  version '0.1'.

Some of this may be pretty clunky, but fixes can be left for later
  * I patched a 'version' declaration into the About text.  This should really be installed as ```thea.__version__```, but I don't know how to reference that from about_window_layout.ui (or however)
  * I changed all the figure refs in user_manual.tex, as it seems all the images have been moved into /docs/resources