* Validates the input to prevent stupid/malicious
* users from corrupting their action file.
*
* Parameters :
* 1 : parameters = map of cgi parameters
* 2 : param_name = The name of the parameter to read
* Validates the input to prevent stupid/malicious
* users from corrupting their action file.
*
* Parameters :
* 1 : parameters = map of cgi parameters
* 2 : param_name = The name of the parameter to read