Introduce templated benchmarks.

[anjagruenheid]

This PR introduces templated benchmarks for BenchBase. In essence, users can define their own query templates that are parametrized with one or more values at runtime. If multiple parameter combinations are possible, we will continue to cycle through all available combinations.

A templated benchmark has the structure

<templates> 
    <template name="$QueryTemplateName">   
        <query>$SQLQuery</query>   
        <types>
            <type>$ParameterType1</type>
            <type>$ParameterType2</type>
        </types>   
        <values>     
            <value>$ParameterValueA1</value>
            <value>$ParameterValueA2</value>
            ...
        </values>
        <values>     
            <value>$ParameterValueB1</value>
            <value>$ParameterValueB2</value>
            ...
        </values> 
    </template> ...
<templates>

where $ParameterType is the integer java.sql.Types value (i.e., 4 for integer, 16 for boolean etc.) and each value tag within 'parameter_values' contains the values for one instantiation of the parameters set in $SQLQuery. The SQL query string is read as a PreparedStatement, i.e., parameters are defined in the string via a '?' placeholder. An example for a templated benchmark can be found in data/templated/example.xml. The file path for the XML template has to be defined in the workload configuration using the 'query_templates_file' tag. An example configuration can be found in config/sqlserver/sample_template_config.xml. The example can be executed if a loaded TPC-C instance is used as JDBC endpoint.

Templated benchmarks are instantiated using 'templated' as benchmark class when running BenchBase via the command line.

[bpkroth]

I think this is ready to go.
It's got lots of tests, both unit and functional for several major DBs now.
The only remaining issue was support for NULLable fields and we filed #366 to track that in future work.