treebrowser: Use consistent capitalization in menu

[medovina]

Before this change, the treebrowser used an inconsistent mix of
capitalized and uncapitalized words in the context menu. This
changes them to all be capitalized for consistency with other
GTK applications.

[elextr]

Maybe you should have reviewed this first.

[medovina]

@elextr, I actually did look at that page while making this change, and generally followed the GNOME guideliines for header capitalization.

I chose to make only one difference from those guidelines: I used the capitalization "Create New File" rather than "Create new File". That's because "Create new File" looks strange to me since "new" is an important word in the menu item.

Is there some other text in this change that you are concerned about?

[elextr]

The New was the one I happened to notice :) And for me the lower case looks better but YMMV, if thats the only case then it doesn't matter.

[medovina]

Actually, looking at this again I think I'd rather change those menu items like this:

Create New Directory -> New Folder
Create New File -> New File

This is shorter and would follow the capitalization guidelines, and is also more consistent with other GTK programs (e.g. Nautilus, gedit). OK with you?

[elextr]

Yeah, folder seems to be more common than directory, and shorter is (mostly) better.