Fix `[x]` in simple table markup

Summary:
This `*` should be a `+` since we want to match //something//.

Fixes `[x]` in a simple table, for any `x` which is not a link.

Test Plan: Added unit test, made it pass.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D5934
Move PhutilArray constructor one level up

Summary: PHP allows changing constructor signature so I see no reason why constructor shouldn't be directly in `PhutilArray`.

Test Plan: Unit tests.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5935