TMSS-2836: added a relational scheduling_constraints_template which allows one unit to be scheduled alongside another unit with a time_offset

TMSS-2847: call evaluate_daily_constraints from get_earliest_possible_start_time_for_daily_constraints with non-gridded timestamp, in order to yield the correct non-gridded earliest_possible_start. Fixed blinking test_triggered_scheduling_unit_unschedules_regular_observation

TMSS-2847: evaluate_sky_min_elevation_constraint returned the incorrect earliest_start_time. Simplified it, and let it work together with get_earliest_possible_start_time_for_sky_min_elevationto better find the actual earliest_possible_start_time for sky_min_elevation

TMSS-2809: only use the known scheduled starttime when evaluating in the same window, else compute a new one

TMSS-2809: speed improvement. do not consider just-placed/scheduled units for the next candidates. unplace only lower score units

TMSS-2809: quite a big refactoring reusing the same methods both for scheduling and placing. Schedule the units in a definable upcoming window (3days), and place the in the remainder of the cycle

TMSS-2809: compute earliest possible starttime and weighted starttime taking used stations into account

TMSS-2577: implemented project/cycle add/update/delete events, and handler, and made the scheduler run on such an event. Added test.

TMSS-2665: check gaps of overlapping stations taking into account the used- available- and specified-stations

TMSS_2638: fixed determine_unschedulable_reason_and_mark_unschedulable_if_needed for time.before and time.after constraints

TMSS-2575: fixed search window issue by enlarging the upper_bound when nothing is found, and by moving the window when found-but-not-scheduled