CB-6344: Specify after which sibling to add config-changes in plugin.xml

* refactor munges - now they are in a more extensible form (munge.files[file].parents[parent][index] { xml, count, after })
* add an after parameter to graftXML which contains a list of possible predecessor elements separated by semicolon
* fix unit tests and add new ones


https://github.com/apache/cordova-cli/pull/157 fixes the tests which failed the previous time these changes got merged.