configuration that does not apply to a particular mojo should be ignored, not fail

this may flow on into plexus, in the form of an option that specifies whether to fail or not.

eg:
<execution>
<configuration>
<mojo1option>foo</mojo1option>
<mojo2option>bar</mojo2option>
</configuration>
<goals>
<goal>mojo1</goal>
<goal>mojo2</goal>
</goals>
</execution>

mojo1 doesn't have mojo2option, but has mojo1option. mojo2 is the opposite. currently, it fails because of this.

the options used, or perhaps any silently ignored, should be output to debug.