Fix https://github.com/julianhyde/optiq/issues/34, "Policy for case-sensitivity of identifiers should be configurable".

New connect-string parameter "lex", with allowable values "ORACLE", "MYSQL", "SQL_SERVER" sets policy to be like those databases, in terms of quote string, whether quoted and unquoted identifiers are converted to upper/lower case, and whether identifiers are matched case-sensitively. It should be possible for each connection to have its own settings for these. Objects shared between sessions (views, materialized views) might require more work.

I've added various internals to make it easy for developers to do the right thing. When you need to look up a schema, table or column/field name, you should use a catalog reader, and it will apply the right case-sensitivity policy. I've removed a few methods that looked up a field without asking for case-sensitivity policy.

Added a mechanism for defining configuration parameters and have them appear in the responses to AvaticaDatabaseMetaData methods.