Fix TypeError when closing tabs with older PyQt-versions.

Fixes #257.

It seems disconnecting a signal from a destroyed object gives us a
"TypeError: pyqtSignal must be bound to a QObject, not 'WebView'" instead of a
RuntimeError with older PyQt-versions (5.2.1).
Update cache size if storage->cache-size is changed.
Add spacing to DownloadView.
Remove unneeded 'except RuntimeError'
hints: Ignore TypeError when disconnecting contentsSizeChanged.

Fixes #263.
Hide 'load glyph failed' Qt warning.
DownloadItem: add successful attribute.
DownloadItem: Add an autoclose attribute.
DownloadItem: Make fileobj public.
downloads: Make it possible to set fileobj instead of name.
downloads: Document _win_id.
downloads: Whitespace change.
downloads: Add a generic NetworkManager.
downloads: Return the created DownloadItem.
configtypes: Handle none_ok differently for List.
Move special network replies to their own file.
configtypes: Add new UrlList type.
Add basic adblock functionality.
configtypes: Add more tests for List/UrlList.
Use statusbar messages for adblock