Horizontal Grammar - Implement control blocks

[thisandagain]

http://www.scratchjr.org/learn.html#blocks

• Wait
• Stop
• Set Speed
• Repeat
• Forever

Depends on #2

[tmickel]

@thisandagain What is this set of issues (#36, #37, #38, #39) referring to exactly?

[thisandagain]

Resolved in c1942bd