Implicit loops

The code to handle implicit loops around expressions that assign to a variable with indices has been greatly improved. Now expressions such as x[i,j+1]=4*y[i,j]**2 will work without having to create array x first. The parser will automagically generate the code required to initialize array x before doing the assignment.
Also array slicing works now. e.g. x[0:10:10]=y[2:12:2] works, with x being created and filled with zeros before the assignment.
See the new screenshot.