Allow script files to be executed as filenames as well as URLs

[keeganwitt]

This feature lets you use this style

<script>${project.basedir}/src/main/resources/groovyScripts/helloWorld.groovy</script>

In addition to the URL style

<script>file:///${project.basedir}/src/main/resources/groovyScripts/helloWorld.groovy</script>

[keeganwitt]

I implemented this by trying

1. as URL
2. as File
3. as script string
   In that order. However, at some point in the future, I may reverse the order of 1 and 2 if 2 becomes the more common usage. The current order was chosen to preserve current performance with existing usages.