lua-calculate-indentation-info: non-functional refactoring

- remove unused parameter parse-begin
- refactor out helper fn `lua-calculate-indentation-info-1'
Fix indentation for blocks starting on continued lines

local foo =
   {
      bar,
      baz
   }  ^
      1. these lines should be indented properly now
^
2. the following lines should be unindented properly now

Two principal changes here:

- continued lines are included in indentation-info

  Previously, continued lines were handled in `lua-calculate-indentation'
  function after block indentation offset was already calculated. This
  prevented proper indentation for pt.1 from above since in that case
  continued-line offset should be applied before block-open offset.

- lua-make-indentation-info-pair no longer folds indentation info

  Previously, lua-make-indentation-info-pair for block-close tokens invoked
  lua-calculate-indentation-block-modifier which returned single pair of
  indentation-info, e.g. (absolute . POS). This was enough for block-close
  token indentation because those're aligned with corresponding block-open
  lines, but in order to indent the following lines properly we need to know
  whether block-open was on continued line or not, so for pt.2 to happen
  lua-make-indentation-info-pair was fixed.

The rest are minor fixes in indentation machinery to accomodate the above.
This should fix issue #33.