dillon1000/react

Lowering for PropertyStore

Converts assignment expressions where the lvalue is a MemberExpression to use 
PropertyStore, rather than creating an lvalue with a member path. The net effect 
is that lvalue will always have a null member path. 

There are two main cases: 

* `x.y = <value>`. We lower <value> to a Place, lower the object of the member 
expression to a place (`object)` create a temporary Place for the result of the 
assignment, and then create a `PropertyStore <object>, "<property>", <value>`. 

* `x.y += <value>` (and similar update-in-place operands). We extract the object 
of the member expression, read the current value via a PropertyLoad, compute the 
updated value, and store it back with a PropertyStore (each of these goes into 
its own temporary).