topbar: Split out properties toolbar

Put properites toolbar code and UI definition into a seperate class and
template, respectively.

https://bugzilla.gnome.org/show_bug.cgi?id=726252
topbar: Split out collection toolbar

Put collection toolbar code and UI definition into a seperate class and
template, respectively.

https://bugzilla.gnome.org/show_bug.cgi?id=726252
topbar: Split out selection toolbar

Put selection toolbar code and UI definition into a seperate class and
template, respectively.

https://bugzilla.gnome.org/show_bug.cgi?id=726252
topbar: Split out wizard toolbar

Put wizard toolbar code and UI definition into a seperate class and
template, respectively.

https://bugzilla.gnome.org/show_bug.cgi?id=726252
Updated POTFILES.in and POTFILES.skip
help: fix missing space in title
headerbars: Remove menubar style class

menubars are a different widget so this style class should not be applied
to header bars. Not using this style fixes padding among other things.

https://bugzilla.gnome.org/show_bug.cgi?id=731426
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Debug comments
Downloading does work now.
TMP
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DRAFT
Temporary commit
Works :)
Nothing big...
Removed unnecessary subprocess, make labelling
Realigned mis-merge