Dashborg-python-sdk

New serialization helpers and options for converting objects to JSON in set_data (and data handlers).

Added two new built in authentication methods:
* simplelogin -- user/password authentication controlled by backend
* simplejwt -- basic JWT authentication for Dashborg panels

Minor updates to the SDK to support new Dashborg server features:
* New expression language for Dashborg code -- https://docs.dashborg.net/reference/expression-reference/
* Templates and Components -- https://docs.dashborg.net/examples/templates/
* Accounts are sandboxed by servername for XSS safety
* New "ui" modes for Bulma, Semantic UI, and Bootstrap
* Updates to example code

Minor Update -- allow set_blob_data to take either a normal or async readable. uses inspect.isawaitable to detect.

Update SDK to support streaming requests, and backend push messages.

* Dashborg now supports streaming requests for long running requests to continually update the UI
* call_data_handler allows backend Dashborg processes to call data handlers in other backend process
* backend_push allows a backend to push a command to waiting frontend clients.
* reflect_zone shows the currently registered procs/handlers for a Dashborg zone

PanelRequest
* Added start_time - time when request started)
* Added is_backend_call - if this request is started from CallDataHandler
* Added is_stream - if this request is streaming
* start_stream() - launches a streaming request from current panel request
* flush() - sends accumulated data/commands to server (used for streaming requests)

dash
* dash.call_data_handler - to call a data handler in a different backend process
* dash.backend_push - to push a command to frontend clients
* dash.reflect_zone - show registered procs/handlers for this zone
* dash.start_bare_stream - starts a disconnected stream (can be connected later using start_stream)

Config
* Added new allow_backend_calls. Set to true to allow backend data calls to bypass panel auth (trusted backends)

Protobuf
* updated to latest protobuf file, includes new RPCs.

Adds image (blob) support
* req.set_blob_data
* req.set_blob_data_from_file