adding DocDB and EasyTables input bindings

[brettsam]

Adds:

• Input bindings for DocumentDB. Non-C# bindings do not automatically update the document when the function exits but you can chain them with another DocumentDB ouput binding to do this. There is an E2E test that does this.
• Non-C# input bindings for EasyTables. The binding will read the item but it is not automatically updated and you cannot chain them with an EasyTable output binding b/c EasyTables performs an insert rather than an upsert. C# is the better language to use if you want to update records.

When issue #49 is resolved, these input bindings will become more useful.

[mathewc]

🚢