Support signature authentication for public links

[C0rby]

Deprecated the changes from #113
and enhanced the api to support signature based authentication for
public links.

[ishank011]

The signature should ideally be returned when calling ListPublicShares as well. Would it make more sense to add it to the PublicShare message?

[C0rby]

The signature should ideally be returned when calling ListPublicShares as well. Would it make more sense to add it to the PublicShare message?

True if we want to introduce this signature authentication in general. I had just had the owncloud public shares in mind which only need the signatures after calling GetPublicShareByToken but I can add that to ListPublicShares.

[C0rby]

Should we always include the signature or should it be controllable via a flag?

[ishank011]

I would prefer that the sign be a part of the PublicShare message. The flag looks fine. Can you just remove the deprecated field altogether? We don't have a lot of clients so breaking changes should be fine at this stage