README: Import README sections from 4.4 branch into master

We had a README file in our release branches, this commit grabs few useful
sections from that file into master's README file.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
CLOUDSTACK-7159 Added "state" parameter to the "listPublicIpAddresses" API call

Signed-off-by: Ilia Shakitko <i.shakitko@tech.leaseweb.com>
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
server: use scoped variable in pom.xml for build.properties file path

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>