GRIFFON-109 remove docs dir when clean is called on a plugin project
GRIFFON-109 remove docs dir when clean is called on a plugin project

breskeby/griffon,codehaus/griffon-git,levymoreira/griffon,codehaus/griffon-git,griffon/griffon,levymoreira/griffon,shemnon/griffon,levymoreira/griffon,shemnon/griffon,tschulte/griffon,griffon/griffon,tschulte/griffon,breskeby/griffon,shemnon/griffon,tschulte/griffon