Multi-Time Trajectory Controller

[henrygerardmoore]

Hello all, this PR serves as a proposal ~~that I plan to bring up in the WG meeting tomorrow (8/14) as well~~ (:white_check_mark: ). The idea is to create a new controller (currently tentatively referred to as the Multi-Time Joint Trajectory Controller or MTJTC, but open to better name suggestions) to meet some use case needs of a client.

Please let me know any thoughts or feedback!