assignemt with indexation doesn't work

[Stan Lagun]

Currently MuranoPL assignment expressions fail when expression uses indexation except for the most trivial cases.
For example neither of the following work

$myDict[$keyName]: value
$myDict['A']['B']: value (even if $myDict['A'] is a dictionary)
$myList[2 + 2]: value
$myList[$index]: value

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/115154

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/115154
Committed: https://git.openstack.org/cgit/stackforge/murano/commit/?id=8a7b2cef50499417f620707ea0f2b282457a2c8a
Submitter: Jenkins
Branch: master

commit 8a7b2cef50499417f620707ea0f2b282457a2c8a
Author: Stan Lagun <email address hidden>
Date: Tue Aug 19 04:06:55 2014 +0400

    LHS assignment expressions didn't work with non-trivial indexation

    Most of assignment expressions involving indexation operator except
    for the most trivial one fail.

    For example the following failed:

    $myDict[$keyName]: value
    $myDict['A']['B']: value (even if $myDict['A'] is a dictionary)
    $myList[2 + 2]: value
    $myList[$index]: value

    This commit adds support for sub-expressions within LHS-expressions

    Change-Id: I4b72e85b5f9bda04c6156d5c8b07eb8f5358643d
    Closes-Bug: #1358545