Re-merge branch 'non-category-modal-editor' into staging

This reverts commit 4c8d8f7bbf83c5de63f0c992e8b109e122e86076.
Fix `grunt mochaTest` errors
Keep blocks static relative to the right edge in RTL mode

This also fixes initial positioning in RTL mode because block position is
corrected during the initial resize of the #blockly div.
Fix jshint and don't reposition blocks if there's no delta
Fix mutator editors inside the modal function editor
Code review feedback
Merge pull request #556 from code-dot-org/fix-rtl-loadblocks

Revised version of PR #550, which was backed out due to `grunt mochaTest` errors