Add support for the new "import *" syntax, and remove support for the "module foo from" syntax.

This only updates the parser and code printer.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=78134363
Use String#intern to avoid creating thousands of copies of strings that show up frequently in JsDoc annotations, like 'string' and 'number'
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=78135478
Make the handler functions passed to IThenable.then nullable.

While the null vs undefined case is not entirely clear in the spec, this follows common external implementations, such as AngularJS' $q, and is generally more idiomatic than passing undefined values before additional parameters in a call.

goog.Thenable which inherits from this already allows the same.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=78180355