Bug 15108: OAI-PMH provider improvements

Bug 15108: OAI-PMH provider improvements

- Fixed date handling to use UTC as specs require.

- Added support for second precision in time stamps.

- Added support for marc21 metadata prefix as recommended in the
  guidelines (synonym for marcxml).

- Improved performance of database queries especially for large
  collections.

- Unified functionality of ListRecords and ListIdentifiers to a common
  base class.

- If items are included in the records, their timestamps are taken into
  account everywhere so that whichever is the most recent (timestamp of
  biblioitem or any of its items) is considered the record's timestamp.

- Fixed OAI.xslt to show correct record range.

- Incorporated extended tests from Bug 17493 and their tweaks from Bug 15108.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Olli-Antti Kivilahti <olli-antti.kivilahti@jns.fi>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>