Fix relative path issues and misc cleanups

Reference:http://www.nabble.com/-VOTE--Releaes-maven-aspectj-plugin-1.1-td20805359.html

Whats left

The string-typed mojo parameters

• aspectDirectory
• testAspectDirectory
• ajdtBuildDefFile
• outxmlfile
  in the various mojos in combination with the construction
  basedir.getAbsolutePath() + "/" + aspectDirectory
  will fail when users specify the parameter value as
  "${basedir}/src/main/aspect". Switching the parameters to java.io.File
  should be sufficient to get proper absolute paths.

Users would benefit if the mojo parameter

• encoding
  would adopt the proposal for source file encoding [0].

The hard-coded site output directory
return project.getBuild().getDirectory() + "/site/aspectj-report";
makes customization quite challenging and completely prevents localized
sites but AjcReportMojo.getDescription() isn't localized anyway...

[0]
http://docs.codehaus.org/display/MAVENUSER/POM+Element+for+Source+File+Encoding

--------
Thanks Benjamin.