Query update APPLY

- Allow applying a function to result sets
- Added apply functions "mixin_add" and "mixin_remove"

````
PHPCRSH> UPDATE [nt:unstructured] APPLY mixin_add('mix:foobar'), mixin_remove('bar:foo')
````

Fixes #99 

Other things we could add:

- `lock`: Lock the node
- `primary_type`: Set primary type
- `lock_refresh`
- `lock_token_add`
- `lock_token_remove`
- `unlock`
- `lifecycle_follow`
- `property_set`: Alternative to `SET a = b`
- `retention_hold_add`
- `retention_hold_remove`