[Users] BRANCH route support

[Juha Heinanen]

Bogdan-Andrei Iancu writes:

 >     - more efficient handling of lumps (changes in request) - instead of 
 > cloning and removing the entire lump tree for each branch, using lump 
 > flags, after each branch, the original lump tree will be just cleaned 
 > only what was added during branch route will be removed).

what if some headers were removed in branch route?  will they be still
there for other branches?

-- juha