Blocks Update - Bug fixes

[stefaj]

This change set addresses the following issues:

• Picture combine (&) and text concat (<>) don't disconnect their blocks anymore - Blocks disconnect themselves when you open the mutator #329. However they do still lose their shadow arguments ((&) loses its shadow parameters when the mutator is opened #309).
• Certain words can be reserved - Blocks lets users use reserved words as variable names #351. Custom words can be reserved with Blockly.UserTypes.userReservedNames in web/js/blocks/init.js. Codeworld functions defined using defineFunction are also reserved.
• Collapsed blocks don't show polymorphic indicators anymore, fixing Collapsing polymorphic blocks still renders the coloring #347.
• A block in the toolbox must now be dragged a certain distance in order to be created - issue Simply clicking once on a block should not place it #327.
• Programs that contain errors can be shared after they are run - issue Blocks should be able to use Share on programs with errors #300

I'm still investigating #337. The effect exists with other blocks as well; the displacement happens to the polymorphic color indicator; however it is the most pronounced with the if block.