Exit codes on error for Rainbow/Tikal

[Former user]

Original [issue 201](https://code.google.com/p/okapi/issues/detail?id=201) created by @ysavourel on 2012-01-17T17:43:52.000Z:

The tools' command line mode (Tikal and Rainbow) should exit with a code when an error occurs.

See http://tech.groups.yahoo.com/group/okapitools/message/2590

[Former user]

Comment [1.](https://code.google.com/p/okapi/issues/detail?id=201#c1) originally posted by @ysavourel on 2012-02-08T16:12:31.000Z:

Tikal already return 1 in case of error. Rainbow command-line mode now also return a non-zero value on error.