npmmojo to allow any npm command without having to write new mojos

A refactoring which prevents you from having to write a new mojo for each npm command. 
You can override with the following config:
<exectuion>
 <i>npm something</id>
 <goals>
  <goal>npm</goal>
 </goals>
 <configuration>
  <command>run something</command>
 </configuration>
</exectuion>

This could enable you to have everything configured with NPM and hence being abel to have any test runner or build tool without having to write a Java class to do it. 

This is a breaking change as the mojo and goal is renamed to reflect the change in behaviour.