Stcrestclient

Addresses an issue with downloading some files via the stchttp.download() API when running the client with the STC REST server on Windows.

Add support for bulk operation APIs. Bulk operations are supported in Spirent TestCenter version 5.12 or later. The `has_bulk_ops` API call is available on `stchttp.StcHttp` to check if the bulk APIs are available.

Bulk API examples are available in the `examples` directory.

- Convert responses to str in python3
- Check for python2.7 or later
- Specify optional download location
- Update help and README
- Allow user to run tccsh and stcinfo as commands

- Adapter `new_session()` takes `existing_session` argument and recognizes `EXISTING_SESSION` environment variable to determine behavior when session already exists.
- Adapter `perform()` recognizes special commands whether or not they have "command" suffix.
- Does not try to use port 8888 on connection failure, which produces confusing error message.
- Provides additional examples passing parameters as kwargs.

In tccsh, parameters for `stc_create`, `stc_config`, and `stc_perform` can have value lists. These are specified as: `param="value1 value2 value3"`. It was not previously possible to specify a parameter with a list of values.

The `create()`, `createx()`, `config()`, and `perform()` methods of StcHttp can optionally take parameters as kwargs. This allows parameters to be passed as items in a dictionary, as keyword arguments, or both.

Check that session has ended

When ending a session, check that the session has ended before returning from the call. This fixes an error that sometimes happened when starting a new session immediately after ending a session with the same user and name.

Automatic file upload in automation wrapper

The automation wrapper now automatically uploads files for additional automation APIs that take an input file argument, if that argument is specified.

stchttp.perform() kwargs params

stchttp.perform() now takes optional parameters, following the command, as a dictionary or kwargs.