Implement associativity, now object literals that are a field value can
start on the same line as the key, like:

a: b:2
   c:3
Remove double-colon operator.  Fix parsing of ^ operator.
Oops, dot should be left-associative, not right associative.  a.b.c ==
(a.b).c not a.(b.c).
Bit of refactoring.
Make sure binary and unary operators have an "op" string to print.
Test case doing a row update using newline/indent instead of curly
brackets.
Covert project into plugin project.  Fix comment parser.  Add source
analyser (used for syntax highlighting and other IDE stuff).
Move banjo.parser.ast to banjo.dom.  Add ExprTransformer system.
Add a visitor pattern for the desugarer to use on the nodes output by
the parser.
Big refactoring
Fix ant build with new package names