MCT Adaptation support for multiple time systems <cubesat issue>

See: https://github.com/NASA-AMMOS/AIT-GUI/issues/212, https://github.com/NASA-AMMOS/AIT-Core/issues/356

MCT has a time system API that may be used to define new time systems based on SCLK, SCET, ERT, etc. This time system API should inherit configured time systems from AIT-Core once that functionality is added. 