file path can ref variables for generate filename.

support filepath ref variable. this is useful for generate filepath or filename.

example:

variables:
package: com.company.project
packagePath: com\company\project
artifactId: helloworld
version: 1.0

filepath1: ${packagePath}\${artifactId}-resource.xml
output1: com\company\project\helloworld-resource.xml

filepath2: ${version}\${artifactId}-resource.xml
output2: 1.0\helloworld-resource.xml

filepath3: ${packagePath}\web\filters\ExampleFilter.java
output3: com\company\project\web\filters\ExampleFilter.java