0.19.0: Merge pull request #178 from rage/reintroduce-urls

tmc-langs-cli

• several commands now take IDs instead of URLs as parameters:
  • download-model-solution: solution-download-url -> exercise-id
  • download-old-submission: no longer takes a submission-url
  • get-unread-reviews: reviews-url -> course-id
  • mark-review-as-read: review-update-url -> course-id and review-id
  • request-code-review: submission-url -> exercise-id
  • reset-exercise: submission-url -> exercise-id
  • send-feedback: feedback-url -> submission-id
  • submit: submission-url -> exercise-id
  • wait-for-submission: submission-url -> submission-id

tmc-langs

• init_tmc_client_with_credentials now takes an URL instead of a String
• download_old_submission now takes a submission_id parameter instead of a submission_url

tmc-client

• removed unused error types
• removed TmcClient::new_in_config
• removed config_dir parameter from TmcClient::new-
• changed TmcClient::new to panic if a trailing slash is missing and one cannot be added to the root URL
• changed TmcClient::{set_token, authenticate} to panic if called when clones of the client exist
• functions that took usize parameters now take u32
• removed all methods that directly access the API from TmcClient and moved them to the new api_v8 module
• replaced old TmcClient::paste with TmcClient::paste_exercise_by_id
• created new api_v8 module that contains functions for accessing tmc-server's API from https://testmycode.github.io/tmc-server/#/
• removed top-level re-exports of response and request types and made the modules public instead
• removed unnecessary re-exports of RunResult and StyleValidationResult
• added docs
• refactored API module

etc

• changed usize to u32 for non-index variables