quattor.build.xml: add support for JSON profiles

- Profiles format defined by property pan.formats (fixed)
- Default directory for profiles defined to build/profiles (instead of build/xml)
- New property build.profiles.dir to define the profile directory name (relative to build/)
- quattor.deploy.and.notify: process .xml, .xml.gz, .json; .json.gz instead of every file found in profiles directory

This is not clear in the commit message but the default format is unchanged (xml).