Re-implementing UnaryExpression to make it more simple
Allowing isNull and isNotNull to accept ExpressionInterface
Remove broken database related features for i18n shell.

The i18n shell has not had any database related features for quite
a while. Remove them until we can sort out how to provide the ability to
seed the i18n tables again.

Refs #3835
Automatically quoting strings passed to isNull and isNotNull

All other methods in QueryExpression had the same behavior so it
made sense to support that here too. Fixes #3836
Merge pull request #3841 from cakephp/issue-3835

Remove broken database related features for i18n shell.
Fix 'either' typo in Time
Fix 'IntlDateFormatter' typos in Time
Fix docblock errors.
Fix url option key.

Closes #3845
Merge pull request #3846 from ADmad/bugfix-3845

Fix url option key.
Merge pull request #3844 from cakephp/3.0-fix-notnull

3.0 fix notnull missing identifier quoting
Merge remote-tracking branch 'upstream/3.0' into 3.0
Tests if _connection is an instance of Connection
This should fixe the Travis build failure
Changed to an isset in case the prefix is 0
Merge remote-tracking branch 'origin/3.0-wip-connection-prefixes' into 3.0-wip-connection-prefixes