Updated volume check action

It will now create the volume element in the XML
if it does not exist. For some reason, Clarity only
returns you UDFs that have a value set. This means
you must create the UDF element yourself when it is
not set. Bizarre.
Removed unecessary comments
Merge pull request #13 from jbeast/vc_fix

Vc fix
Modified to use unicode character for micro
Merge pull request #1 from mgcam/devel

command line and user friendly option for choosing source or target plates
Modified XPath to find PerAllInputs
Merge pull request #12 from jbeast/print_setup

Print setup
tests for volume check;  utf8 encoding when caching XML files; some common methods and accessors moved from the volume check to the epp parent; create_label callback to call parent run method