* modified simple creator plugin to be able handle version control
* added 'allow_version_control' to simple creators
* don't remove 'create_context' from pyblish context during publishing
* implemented validator for existing version override
* actually fill version on collected instances
* version can be again changed from standalone publisher
* added comment to collector
* make sure the version is set always to int
* removed unused import
* disable validator if is disabled
* fix filtered instances loop