Bug 3881: OPAC Privacy reimplementation

Bug 3881: OPAC Privacy reimplementation

Reimplements Paul Poulain's original OPAC Privacy patch, with some minor improvements and changes to wording

If the library enables the OPACPrivacy system preference along with the opacreadinghistory preference, and sets
an AnonymousPatron (must be a valid patron number in the database), the user will see a new tab upon login to
the OPAC, My Privacy.  From there, the user can:

- Set their OPAC Privacy to one of three values
  0 - Forever.  This keeps their reading history unless they explicitly delete it; the bulk anonymiser won't touch it
  1 - Default.  Keep reading history until either they delete it or the library does
  2 - Never.    Instantly anonymises reading history upon item return

- Instantly delete their reading history
  There is a warning and a popup to confirm.  I've removed Paul's extra confirm checkbox, which seemed redundant

A note of which preference the patron has selected is added to the Patorn Details page in the staff client.  This is read-only.

This patch also consolidates Privacy system preferences into the Privacy section of the OPAC tab.

Thank you to BibLibre for the original implmentation of this patch, and Los Gatos Public Library for funding and
testing the reimplementation.

Signed-off-by: Nicole Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>