Sqlite / SQLAlchemy: enforce Foreign Keys
Fixes #1075
Fix connection parameters for sqlite through sqlalchemy.
implement insert or ignore database statements
Avoid duplicates in missing hashes reports.
fix bugs in dbwrapper
Make AlchemyBackend a ModularBackend module.
Make modular backend load modules dynamically.
Add index on versions table.
Fix blocker.
Fix hash map PUT conflict.
Return paths shared to '*' in shared lists (in simple and modular backends).
Merge branch 'master' of https://code.grnet.gr/git/pithos
modular backend: set node indexing on version table instead of node table
Fix virtual folders.
Update documentation.
Modular backend progress VI (release).
Modular backend progress V.
Modular backend progress IV.
Modular backend progress III.
Modular backend progress II.
Modular backend progress.
First commit of Node module (backend module doing path management, versions, metadata).
Move hashfiler to backends folder.
Modular backend alpha release.
More modular backend.
Start of modular backend (not working yet).