add README in directories and fix scripts •move plugins_ext to src/plugsin_ext to be parallel with internal plugins
add README in directories and fix scripts
•move plugins_ext to src/plugsin_ext to be parallel with internal plugins

imzhenyu/rDSN.dist.service,imzhenyu/rDSN.dist.service,imzhenyu/rDSN.dist.service,imzhenyu/rDSN.dist.service