Implements a DELETE API endpoint for stopping a graph monitoring process and refactors the graph API tests

Updates graph_monitor API endpoint to also save the request identifier and the pipeline process identifier

Implements and tests an addition to the response of the build request for a temporal graph - now the list of endpoints is also returned

Refactors tests for handling invalid requests and adds new tests for the execute pipeline API endpoint

Updates graph build API endpoint - timestamps are now passed in the JSON body and not in the URL query string

Added a function to generate the network topology given the switch-to-switch links, switch IP addresses and cluster-to-router mapping; changed ComputeNode to Cluster; added Switch nodes; modified tests

Updates the graph build API endpoint to also include service function chain and service function chain instance