Few Enhancements. See description.

- Added `deploy-dir` target for deploying multiple web-apps from
directories specified in parameter `source`. Source parameter can be a
comma-separated list of directories. Each directory can be relative to
the project base dir or absolute.
- Added support for parameters in the configuration section of the maven
plugin. So nwcloud.properties can be omitted.
- Added support for parameter `vm-argument` in `nwcloud.properties`.
- Added support for parameter `compression` in `nwcloud.properties`.
- Added support for parameter `compressible-mime-type` in
`nwcloud.properties`.
- Added support for parameter `compression-min-size` in
`nwcloud.properties`.