Add http operators supporting streaming reads etc about streamsx.inet

[hildrum]

Hi Rohit, for the record, can you state that this is code you wrote and have leave to contribute?

[rohitsw]

This code has been written by me and was approved and available on developerworks as HTTPUtils package. The source code checked into github is a variant of that codebase with minor updates and cleanup.

[ddebrunner]

Looking a the current code, the operators don't have any description. Will you be adding some before the pull request? Just trying to understand how the streaming HTTP operator differs from InetSource.

[ddebrunner]

Should the model files be checked in? Since these are annotated Java primitive operators the xml files are generated. For the Java operators i added, I didn't check them in, though I think I need to add entries to gitignore for them.