Added Identifier classes, tweaked directory structure

F1ST P0ST!!

So, here are the very first classes for our AST/Interpreter tree hybrid. A few points of discussion

 - Do we need the typical java `src/org/whdl/fontend` directory structure?
 - I made an assumption that we want to have different syntax for navigating the namespace hierarchy than we do for navigating tuples (ie `whdl::Integer.foo.bar` vs `whdl.Integer.foo.bar`). I'm willing to go the other way on this but it'll make name resolution harder and potentially introduce weird behaviour for devlopers.
 - Should we have an inline documentation standard (ie docblocks?)

And some follow ups

 - The next accepted pull request ought to be a build/testing setup that, at the very least, ensures this code compiles and tests the accessors.
 - We will make some kind of glossary of terminology for the codebase as to encourage consistency in naming
 - We will continue adding points to the coding standards as they become relevant
 - We will start developing some formal procedures around pull requests