Set Canvas Manual grade posting policy

[kitsook]

With the launch of new Canvas gradebook and demise of the "muted" parameter of assignment api, changed the way how grades are pushed to Canvas:

• add a new component for Canvas GraphQL API calls. The implemention is a thin wrapper on existing RESTful API. Doesn't handle pagination etc complicated logic
• set newly created assignment with manual grade posting policy
• add / change description on the iPeer page to remind instructors to manually post the grades in Canvas

Bump version to 3.4.4

Closes #622

[kitsook]

Closing this PR. Changes to be included in #629