[Qt] minor watch-only changes

- use watch-only, not watchonly
- add back a tooltip hint when hovering addresses and attach
  "(watch-only)" at the end
Merge pull request #4783

fbe0fca [Qt] minor watch-only changes (Philip Kaufmann)
depends: fix typo in source downloading. Regression from c897b1e732.

Some sources are renamed after download, since the filenames don't play nice
with (for example) gitian. This fixes the rename.

Needed for OSX build as it renames a file.
travis: add osx build