system messages referring to contacts should be tappable

[r10s]

currently, system messages show name+email address in their text, eg. sth. as
Member Alice Atkinson ([email protected]) added by Bob Butler ([email protected])

this not only makes the message hard to read - it could be just ...
Member Alice Atkinson added by Bob Butler
... - the email address in general is not the only criterion to identify a person, and not the most important one. chat history and shared chats, acceptance etc. are at least equally important.

therefore, we should change the strings in core - and at the same time change UI to open the contact profile when tapping the system message:

• for "Group image changed by ..." and Group name changed by ...", "Disapparing messages changed ..." the contact_id is from_id
• for "Member ... added by ..." and "Member ... removed by ...", we probably need a new API, as the added/removed member is of major interest (from the profile on can easily check "introduced by" and see who added the member)

finally, to close this issue, the correct info type needs to be set also for received info messages and the additional info types need to be documented (currently, only few info types are used externally)