Added common open source licenses.

Use <header>LICENSE</header> inside the plugin's configuration element
to specify a license. Example: <header>APACHE-2</header>

Signed-off-by: Sebastian Hoß <mail@shoss.de>
No need to declare extra dependency anymore.

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Merge pull request #25 from sebhoss/licenses

Added common open source licenses.