Exclude static flyouts from blockspace metrics (fixes modal editor in non-category mode)

We use two types of flyouts in the block toolbox:
1. Static flyouts for the non-category toolbox
2. Dynamic flyouts that appear when a category tree item is clicked

Prior to this change we treated both the same when calculating blockspace metrics.  For non-category mode, this meant the blockspace extended under the static flyout.  Blocks were shifted to the right in the main blockspace by manually adjusting the blockspace canvas `<g>` element (see https://github.com/code-dot-org/code-dot-org/commit/74941cf043a419ae83c9b01b3c0ad39fe532dda0#diff-44858d19546fe7485d7fa3b235e62898L339).

This change moves the blockspace boundary from the **left edge** to the **right edge** of static flyouts.  The blockspace boundary for dynamic flyouts is unchanged.

Before: (the blockspace boundary is marked in red)
![screen shot 2014-11-24 at 4 14 10 pm](https://cloud.githubusercontent.com/assets/413693/5175974/0a522b86-73f7-11e4-99e8-243c1da08e66.png)

Fixed with this change: (the blockspace boundary is marked in red)
![screen shot 2014-11-24 at 4 14 38 pm](https://cloud.githubusercontent.com/assets/413693/5175975/0ba39934-73f7-11e4-8f14-7e72c1a1bb67.png)
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