[magneto/gtk*] fix string format in both gtk2 and gtk3 frontends
[entropy.client.dep,solo] add support for --onlydeps, as per bug #3817

equo {install,source,download} now support --onlydeps.
Using --onlydeps, only dependencies of the selected packages are installed,
unless the selected packages are dependencies themselves.
[entropy.client.dep] use set.clear and dict.clear instead of del
[equo] update man pages