Enforcement

[atz]

Changes appear larger than they actually are, but include:

• Correct comment about solr_access_filters_logic params
• Un-protect discovery_permissions getter/setter
• Use attribute and alias declarations where possible
• Lots more YARD doc for all
• Delete #except and #append tests, these were testing SearchBuilder, not Enforcement. Apparently the methods existed in Enforcement once, but were deleted. The tests remained and still passed, so that gives you an idea of how useful they were.
• Stop testing SearchBuilder, start testing a class including the module. That class represents our downstream consumers, not SearchBuilder.
• Additional tests for a couple basic operations and exclusion of empty clauses

[atz]

@jcoyne Corrected the typos and added replies to your comments.

[atz]

@jcoyne updated that comment