Support case-insensitive string matching

[Firehed]

Currently, the internal behavior varies from common database interactions (at least MySQL) where criteria are evaluated using case-sensitive string comparison functions, but the storage backend may be done in a case-insensitive way. This can result in behavior that's confusing and misleading, and necessitate (at best) overly-brittle tests.

For text columns, it's probably best to do case-insensitive comparisons (binary columns should remain case sensitive). Ideally comparisons would match the same collation as the backing storage engine, but that's significantly more complex to implement and of diminishing added value.