Bug 6390: Implement 'see mine/my branches/all baskets'-syspref

Bug 6390: Implement 'see mine/my branches/all baskets'-syspref

Code written by Edgar Fuß <ef@math.uni-bonn.de>,
Mathematisches Institut der Uniersität Bonn

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
- rebased on current master, fixed a conflict in booksellers.pl
- reworked permission checks to account for general acq permissions and
  superlibrarian permission
- rephrased text of system preference (Thx to Jared Camins-Esakov)

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>