Add a .gitignore file

Ignore .amx file (compilation results)

Signed-off-by: David Wagner <david@marvid.fr>
Conway: cleanup and add BSD license

Signed-off-by: David Wagner <david@marvid.fr>
Simon: change license to BSD

Signed-off-by: David Wagner <david@marvid.fr>
Remove GPL license (now using BSD)

Signed-off-by: David Wagner <david@marvid.fr>