Support creating SAS for Azure stoage services

1. Support new commands
   * azure storage container sas create
   * azure storage blob sas create
   * azure storage table sas create
   * azure storage queue sas create
2. Fix bugs: some of storage unit tests cannot be run live
  
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permissions is a string, right? So string.split results in an array. You should never use a for-in loop on an array - see http://stackoverflow.com/questions/500504/why-is-using-for-in-with-array-iteration-such-a-bad-idea and https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in or the Good Parts book for details.