Update of joda-time library (from 2.1 to 2.6) to support timezone changes.

This is *joda-time* library upgrade, since we have experienced a problem with running some of your tests, that depends on old joda-time. More precisely, *TimeExpressionTest*. The cause is in time zones changes from 2.1 joda-time release. This is not cirtical, because we just can exclude the lib with maven *exclude* directive and push the new one, but, I suppose it's better to have the fresh one.