SQL syntax validation

[Alex Boyko]

Currently MySQL grammar is used for semantic tokens and syntax validation for the native queries.
However, there are more flavours of SQL available: PostGres, MariaDB, etc (see https://github.com/antlr/grammars-v4/tree/master/sql)

Perhaps an inference can be made from the classpath JARs to indicate which SQL parser should be used... Perhaps we may want to opt out from supporting native query syntax validation completely (too much for a rather limited use case), perhaps the same is true for semantic tokens... The most commonly used ones might be supported and for the rest no syntax validation... TBD