LP#1729620: Polish up sets and visibility tests

LP#1729620: Polish up sets and visibility tests

This commit improves the logic needed to control record inclusion in
OAI Sets.  Sets for bib records are currently based on copy visibility,
Located URI visibility, or bib source.  Generally useful combinations
are generated for item, Located URI, and transcendant [sic] bib sources.

Sets for authority records are based on the browse axis of the heading
for the record.

All generated Sets for bib records currently test for effective search
visibilty on the three described components.

In order to retrieve item data from a specific branch of the org tree,
a harvester must use a Set that contains COPIES:. The hierarchial
shortnames of the org units follow the colon, so in a freshly installed
system a Set with the setSpec of COPIES:CONS:SYS2:BR3 will retrieve all
bib records that have visible copies at BR3, and include only the item
data for that org unit.

To retrieve records with Located URIs, which behave in the heirarchical
reverse of copies by limiting display to those org units "inside" the
branch of the tree where the licensing "lives", a harvester should
supply a setSpec with an org unit shortname that would display the
Located URI. For example: LURIS:CONS:SYS2:BR3

Note: the LURI: org unit is also used to restrict any item data that may
be available for LURI-filtered records.

To retrive records are in a transcendant [sic] bib source, a harvester
can used a setSpec starting with SOURCES: followed by the source name.

To harvest all records, including deleted records, simply omit the
setSpec from the request.  All item data will be included.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Jane Sandberg <sandbergja@gmail.com>