refactored unit tests
upgrade crate testing instance and crate client to 0.42.0
implemented batch execution

on CrateStatement and CratePreparedStatement
Merge pull request #26 from crate/m/bulk_args

M/bulk args
use bulk operation if crate server supports it
Merge pull request #27 from crate/m/version_aware_bulk

use bulk operation if crate server supports it
use SQLBulkRequest to execute batch queries if supported
added JDBC compatibility docs
Minor doc change
correctly mark no-op method
move server version to DatabaseMetaData
update driver version to 1.1.0-SNAPSHOT for feature branch
Merge pull request #30 from crate/executebatch

execute batch
updated to crate client version 0.42.1