Upload configuration file

Allows to automate the upload of a single solr config file. 

1. ​POST https://opensolr.com/solr_manager/api/upload_config_file
2. Parameters:
   1. ​email - your opensolr registration email address
   2. api_key - your opensolr api_key
   3. core_name - the name of the core you wish to upload the schema.xml for
   4. userfile - your local schema.xml file to POST and upload to the server
3. Example here: https://opensolr.com/solr_manager/upload_config_file_form