Closes #2761

* add x-cassandra
* add support.doubleQuote
* add support.commentSlashSlash

* add support to "charsetCast" with syntax n str or N str or _charset str
* add example in index.html

* index.html included codemirror.js twice
* optimize .tableName syntax check

Closes #1489

* mysql & mariadb:
** .21 syntax
** .table_name syntax
** added keywords
* MIMEs define their operatorChars
* MIMEs have a support prop
* use spaces as tab in index.html for consistency
* some return false -> null
* more comments

* standard SQL syntax for date/time/timestamp values
* ODBC syntax for date/time/timestamp
* added new syntax in index.html