add TODO, tests and some small fixes

add TODO
add a bunch of tests
fix issue where 'order by' was being confused with the 'or' operator
  due to bad lexing
fix missing ctor in parens scalar expr parser
rename parens scalar parser to sparens and betweenParens helper to
  parrens
export the makeSelect from the syntax module

TODO

@@ -0,0 +1,68 @@
+add tests
+
+left factor parsing code
+
+implement pretty printer
+
+reimplement the fixity thing natively
+
+dialect switching
+
+fix lexing wrt suffixes
+
+position annotation
+
+emacs parse error formatting
+
+= sql support
+
+count(*)
+decimal literals, split string and number literals
+order by directions
+distinct/all
+limit,offset, top
+
+scalar function syntax:
+  aggregate app
+  window app
+  cast
+  exists, in subquery
+  scalar subquery
+  in list
+  any/some/all
+  between
+  is null/ is not null
+  review all ansi sql operators
+  interval literal
+  typed string lit?
+  placeholder/positional arg
+
+other missing operators
+  unary + -
+  row constructors?
+  extract
+  substring
+
+except, intersect, union
+
+
+review identifiers
+order by nulls first/last
+extend case
+more dots in identifiers
+escapes in string literals
+full number literals
+quoted identifiers
+group by (), grouping sets(), cube, rollup
+lateral
+corresponding
+named windows
+cte
+apply, pivot
+full tableref aliases
+collate
+
+within group aggregate syntax
+try to do full review of sql2003 query syntax
+
+maybe later: other dml