Release 0.58

• Add first version of Cassandra connector. This plugin is still in development and is not yet bundled with the server. See the README in the plugin source directory for details.
• Support UDFs for internal plugins. This is not yet part of the SPI and is a stopgap feature intended for advanced users. UDFs must be implemented using the internal Presto APIs which often change substantially between releases.
• Fix Hive connector semaphore release bug.
• Fix handling of non-splittable files without blocks.