Provide a paste.create Conduit method

Summary:

• Allow the console to handle abstract classes correctly.
• Move paste dictionary generation to an abstract base class.
• Add paste.create.
• Add 'objectName', 'parentPHID', and 'content' to Paste info dictionaries

(you can use filePHID with file.download to get the content but I think just
always sending it back is reasonable).

Test Plan:

• Use paste.create to create new pastes.
• Used paste.info to get existing pastes.
• Checked console UI to make sure "paste." didn't show up or anything

silly/dumb like that.

• Tried to call the method "paste" and got the right exception.

Reviewed By: codeblock
Reviewers: codeblock, jungejason, tuomaspelkonen, aran
CC: aran, codeblock
Differential Revision: 747