Added nested parameters and substitution properties to AbstractLiquibaseTask.

Usage is:
<liquibase-update ...>
  <parameter name="logLevel" value="info" />
  <property name="idtype" value="INT" />
</liquibase-update>

Which results in:
liquibase ... --logLevel='info' update -Didtype='INT'
Added a generic LiquibaseTask.
With nested parameters in AbstractLiquibaseTask, all we need is the command.