fixes #20 by adding support in the planner for array flattening and fixi...

...ng some bugs in the logical plan compiler. a couple tests had to be disabled which currently have ambiguous compilation targets: select foo{*} and select foo.* are compiled to the same AST, but the former has a meaning specific to MRA (equivalent to foo[*] but for objects), while the latter has a meaning specific to SQL (qualified selects). further work is needed to support both of these constructs, probably beginning in the parser.