Multimodal Insertion Heuristic prototype

See merge request !1

(TODO: add requests variants with some successes and some fails)

update PT Line parser format to control travel time + implement fixed schedule parsing and add parser docs

(for now always true, TODO:add to request import format)

if request was unfulfilled, emplace its ID for future reference to insert it via SAEV-only best insertion in the last step of algorithm

separate bound propagation method from insertion method to allow propagating changes from a given bound queue

(it used to create multiple side effects wrt request pointers and how we access base/sub requests)

TODO: handle diverse fail/unfulfilled cases wrt list size, isEntry etc