Merge pull request #42 from cbhaley/master

Fix problems creating template functions caused by the changes for the new single-name rule
Allow using a tweak to switch db backends
Use the correct metadata backup implementation
Missing legacy API
Replace use of db.conn.close() as it is not supported in the new backend
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Accidentally ignored commit_dirty_cache()
Speed up book list rendering by using the new api to get values
Clear the composites cache correctly
Restore getting the size value to old behavior
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Fix refresh_ids() and rendering of size and datetime fields
Add tests for composite cache invalidation
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Implement reinit_db() with apsw
pep8
Minor fixes
New API version of library check
When reloading on dn modification, re-open the connection

This ensures that the content server does not continue to use a deleted
metadata.db.
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