Edit WebSubmit Function

This function compares the content of a file to different values and
directly goes to a different step in the action according to the value.

This function may be used if the treatment to be done after a
submission depends on a field entered by the user. Typically
this is used in an approval interface. If the referee approves
then we do this. If he rejects, then we do other thing.  More
specifically, the function gets the value from the file named
[casevariable] and compares it with the values stored in
[casevalues]. If a value matches, the function directly goes to
the corresponding step stored in [casesteps]. If no value is
matched, it goes to step [casedefault].

@param parameters: (dictionary) of parameters (relating to the given
 doctype/action) that are to be passed to the function:

    + casevariable: This parameters contains the name of the
                    file in which the function will get the
                    chosen value.
                    Eg:"decision"

    + casevalues: Contains the list of recognized values to
                  match with the chosen value. Should be a
                  comma separated list of words.
                  Eg:"approve,reject"

    + casesteps: Contains the list of steps corresponding to
                 the values matched in [casevalue]. It should
                 be a comma separated list of numbers.
                 Eg:"2,3"

                 In this example, if the value stored in the
                 file named"decision" is "approved", then the
                 function launches step 2 of this action. If it
                 is "reject", then step 3 is launched.

    + casedefault: Contains the step number to go by default if
                   no match is found.
                   Eg:"4"

                   In this example, if the value stored in the
                   file named "decision" is not "approved" nor
                   "reject", then step 4 is launched.

@return: (string) - empty string