L10N - Fix RTL rendering of blocks

[thisandagain]

In the process of quickly implementing the horizontal grammar we broke RTL in a number of places:

Depends on #31

[rachel-fenichel]

@carljbowman what's the reference point for positioning the icons? (Start, end, centered, etc.) Are we ever going to have horizontal blocks that could have multiple icons? Will there be C-shaped blocks that have an icon at the beginning instead of the end?

@NeilFraser should I try to make this generalizable (for horizontal blockly with arbitrary blocks/arbitrary numbers of images) or implement it specifically for the scratch jr cases?

FYI in the existing code "icon" refers to the little gear for mutators, exclamation mark for the few errors, etc.

[NeilFraser]

Blockly attempts to be general-purpose. No matter what Frankenstein block configuration you give it, Blockly will render it properly. But the result is a rather complicated codebase.

Scratch Jr has an exceedingly small number of shapes. Therefore I think it is best for Scratch Jr to take the more limited approach of just rendering what it needs to. This leads to simpler code, though every time a new block shape is added (e.g. if/else), Scratch Jr will need more code. Since Scratch Jr does not have an open-ended set of blocks, non-generalized code should be an easier path in my opinion.

Scratch on the other hand is much more expressive and should be fully generalized.

[rachel-fenichel]

Not fully there yet.

[tmickel]

yeah, that automatic closing gets you sometimes :P

[tmickel]

Still to do: rendering the field/input in the right place.

[tmickel]

Closing this now as it's actually fixed I think. Let's revisit in new bugs if there are new problems.