px:copy-resource generates random filenames when used with xproc-maven-plugin

`px:copy-resource` works fine in Pipeline 2. However, when using it with xproc-maven-plugin and xproc-engine-calabash, it generates a bunch of random filenames instead of using the correct filenames. For instance, this is the relevant XProc snippet:

``` xml













































```

The file `file:/tmp/store-resources.xml`, after running mvn clean test in the project which includes a xprocspec test that runs this code, contains this:

``` xml

file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/calabash2374172372135276858.css
file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/fonts/opendyslexic/calabash4617965847886900536.saveme
file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/fonts/opendyslexic/calabash6051939913266286017.saveme
file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/fonts/opendyslexic/calabash3661913066972083891.saveme
file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/fonts/opendyslexic/calabash5265507794635387704.saveme
file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/fonts/opendyslexic/calabash2376770965136006182.saveme
file:/home/jostein/nordic-epub3-dtbook-migrator/target/xprocspec/tmp/xprocspec-20150115165940686/temp-dir/html/css/fonts/opendyslexic/calabash740651197898919601.text

```

So the files are copied, but either calabash or Java seems to do some guesswork as to what the filename should be. It identifies a css file and a text file, and the rest are stored with a "saveme" file extension as they are probably identified as just binary files.