Add comparison check to DatabaseConfig class.

This adds a custom '==' operator to the DatabaseConfig class to resolve
possible issues when trying to match an existing connection pool with a
fresh config file.
Have database list objects pass on credentials when copied.

This causes the DBDataRef class to pass on its stored DatabaseConfig
object when duplicating itself, preventing the new class from having to
reread the config.xml to discover the database.

Signed-off-by: Raymond Wagner <rwagner@mythtv.org>