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