When task and form variables have different names, the freemarket template form
generated for a user task references process variables, therefore causing a
runtime parsing error.
Furthermore, when a variable is both used for input and output, its value is
not provided for users to edit and they are forced to copy and paste it from a
table above.

Version-Release number of selected component (if applicable):
dev6

How reproducible:
Consistent

Steps to Reproduce:
1. Create a process with a user task that has different variable names than the
process variables
2. Click on the user task and use the toolbar button "Generate Task Form
Templates"
3. Run the process and view the task

Actual results:
HTTP 500 error, see attached FreemarkerError.jpg

Expected results:
Task form that shows input variables as read-only, has a blank field for typing
output variables and shows the value of in/out variables so they may be edited.