QS-2885 done -- multi-dispatching mechanism for ECL commands

To use dispatching, call the ServiceDispatchingUtils.handleWithExtension method. Then you can provide an IScriptletExtension implementation by registering it in org.eclilpse.ecl.dispatch.scriptletExtension extension point.

See the scriptlet-extensions branch for details.

Squashed commit of the following:

commit 4fa4f6bdd31469f7de0c394bc79df38e47977ac6
Author: Alexander Sheboltaev <alexander.sheboltaev@xored.com>
Date:   Thu Sep 5 15:21:14 2013 +0700

    QS-2885 :: updated the poms & the feature for the new dispatching plugin

commit 0268ccf396915cda2057cbee887b366ba4056a79
Author: Alexander Sheboltaev <alexander.sheboltaev@xored.com>
Date:   Tue Sep 3 18:11:16 2013 +0700

    QS-2885 :: checking extension ability & uniqueness

commit 7c552238980706c6b59e82c6120e21e4338c22e9
Author: Alexander Sheboltaev <alexander.sheboltaev@xored.com>
Date:   Tue Sep 3 17:22:23 2013 +0700

    QS-2885 :: handling multiextension case by taking the first available

    But storing all of them in a ScriptletExtensionPack.

commit 38d6692fdada4d2ae2fbeff7c98fa139eda26c30
Author: Alexander Sheboltaev <alexander.sheboltaev@xored.com>
Date:   Tue Sep 3 16:11:57 2013 +0700

    QS-2885 :: scriplet extensions dispatching initial implementation