db structure, allow null in columns for '' values
shorten table identifiers in tests
add missing backticks all over the place

Conflicts:
	apps/files_encryption/lib/util.php
	lib/files/cache/backgroundwatcher.php
	lib/files/cache/cache.php
fix fetchRow checks to also work with MDB2
convert LIMIT to parameter
allow install when only oracle is available
oracle fixes, missing backticks, LIMIT to param

Conflicts:
	lib/files/cache/cache.php
use to_char only for oracle, whitespace
cleanup codestyle
don't use sequence suffix, MDB2 handles that internally
Merge pull request #3725 from owncloud/oracle_stable5

Oracle stable5