Added test/functional to _Events.groovy defCloverSrcDirs list

If the test/functional directory is not included in the clover plugin, the functional tests results will not be included in the Clover report and the plugin code needs to be edited directly (boo!). 

I found this out by using the Grails plugin but could not find the source code on github so I editid this plugin instead. 

Thanks!

Michael
This change looks OK. The toggleCloverOn() method has a protection against non-existing directories:

{code}
cloverSrcDirs.each {dir ->
                if (new File(dir.toString()).exists()) {
...
}
{code}

so presence of test/functional directory is not mandatory in projects.