Merge QUrl::DecodeAllDelimiters and QUrl::DecodeUnambiguousDelimiters

Merge QUrl::DecodeAllDelimiters and QUrl::DecodeUnambiguousDelimiters

There's little value in having the DecodeUnambiguousDelimiters option
since neither QUrl nor QUrlQuery can return values that are ambiguous
in that particular context, ever.

This option could be used to encode a character if, when placed
in a URL, it would need to be encoded. Such cases are hash (#) or
question marks (?) in the path component, or slashes (/) and at signs
(@) in the userinfo.

However, we don't need two enums for that, since there are no
other characters that can appear in either form. Still, leave two bits
for this enum. In the future, if we want to split the gen-delims from
the sub-delims, we are able to.

Change-Id: If5416b524680eb67dd4abbe7d072ca0ef7218506
Reviewed-by: Shane Kearns <shane.kearns@accenture.com>