Make rank_ou org unit sorting function more broadly applicable

[Bill Erickson]

This branch attempts to give the org unit ranking function evergreen.rank_ou() broader applicability. The two practical differences between the existing rank_ou and this new implementation in regard to the TPAC are:

1. Pref lib plays a role in sorting even when not searching at CONS. For example, searching SYS1 with a pref_lib of BR1, items at BR1 will sort ahead of items at BR2.

2. It also adds handling for the following special case where the pref lib is a child of the search lib: Searching CONS with a pref lib of SYS1, items at BR1 and BR2 will sort ahead of items at BR3.

Note that when searching a specific branch, search lib still trumps pref lib.

From the commit: ----------

When determining how to sort an org unit (e.g. sorting copies by circ lib for display in the catalog), allow the pref-lib to affect the sort order in global and non-global searches.

Org units are now sorted with the following criteria in the following order. For example, assume we are sorting a copy circ_lib:

1. circ_lib matches the search_lib

2. circ_lib matches pref_lib

3. distance of circ_lib from pref_lib when pref_lib is a child of search_lib, if circ_lib is a child of pref_lib. (For example, searching CONS with pref_lib SYS1, items at BR1 will sort ahead of items at BR3, since BR1 is a child of the pref_lib).

4. proximity of circ_lib to search_lib, when circ_lib is a child of search_lib.

5. In all other cases, circ_lib is sorted to the bottom with the rest of the riffraff.
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working => user/berick/expand-rank-ou-func

[Ben Shum (bshum)]

Seems to work fine for me so far. Continuing testing.

[Ben Shum (bshum)]

Picked to master.