JCLOUDS-61 License header update in jclouds/jclouds-labs

https://issues.apache.org/jira/browse/JCLOUDS-61

updated pom.xml and src/etc/header.txt, removed malformed or duplicate headers
then executed
```
mvn com.mycila.maven-license-plugin:maven-license-plugin:remove
mvn com.mycila.maven-license-plugin:maven-license-plugin:format
mvn clean install
grep -R 'Licensed to jclouds, Inc.' *
```