implement report configuration

notes:

• if in <reports> the configuration applies to the report, which may be different to the mojo in <build/> if the plugin is executed there. So we need that separate section.
• currently, the report is not configured at all, as we use a map lookup

implementation:

• similar to executeMojo, a getReport method should get a configured MavenReport
• remove the MavenConfiguration inline with this, AbstractMavenReport should have a outputDirectory and project field. due to the way locales are done, this will moving the output directory creation into the abstract report where it can concat the locale
• reports should be configured from the <reports/> whether they are being executed or as part of the site, not in <build/> like normal plugins
• design as shown here: http://docs.codehaus.org/display/MAVEN/Multiple+Goal+Declaration, ie:
  <report>
  <g/a/v>
  <configuration />
  <reportSets>
  <reportSet>
  <id />
  <configuration />
  <reports>
  <report>...</report>
  <report>...</report>
  </reports>
  </reportSet>
  </reportSets>
  </report>