Populate Text(58) field when rejectMessageOnUnhandledException=true

[mgatny]

Supersedes #667
refs #639

If rejectMessageOnUnhandledException=true and an unhandled exception is thrown from the fromCallback(), include the exception message in the Text(58) field of the resulting Reject or BusinessMessageReject.

[chrjohn]

@mgatny thanks for the PR.
The only thing that troubles me is that it might reveal internal information about the application e.g. "Out of memory" or similar. What do you think about adding a prefix like "error: " or "problem: " to the Text field so that users could possibly filter out such messages in their toAdmin() or toApp() callbacks?