Fixes: #36 #37 #38 #40 #41 + Subpackages page works

[boyks]

1. Small stars near labels on import page - I think they look pretty.
2. User won't be switched to next page until he'll provide path to existing file or directory, if doesn't exist - on click "Next button" page will not be switched and import filed will be highlighted (looks better now)
   + same highlighting works while user typing path (-> pathlib used).
3. Subpackages works now (files from left side moves to the tree of sub-packages) - only thing I'll need a list of files that could be added to sub-packages.
4. About importing directory - right now I can't find cool way to work it out with one button (so I came up with those two - another way was radio buttons, but later I'll figure out how to do it with one button) - just there is no standard function for doing this.

[jsilhan]

hey, you did what I wanted but that fields looks ugly aren't they? can we preserve the background and only add red border?
Now I see that only bolding text labels for required fields would be better. Red borders (with default background preferred) could be used for validation of fields according to Fedora conventions later. Sorry for change.

[jsilhan]

Also next time use one commit per issue, please.

[boyks]

Yeah, after I did pull request I mentioned that they don't look pretty cool. So I already remade them. Now they look a bit different way you've described (near the name of label there is a small red star), I think it looks pretty good, tomorrow I'll make pull request for it.

[jsilhan]

Now that border looks cool although it changes the height of field so the bottom fields are jumping. I've taken two import buttons as temporary solution. Merged, thanks.