Support for non-PT sims

[KasiaKoz]

Trying to run elara on a sim with no PT fails with it asking for a transit schedule:

07-15 10:57 elara.config DEBUG Building Tool GetTransitSchedulePath
07-15 10:57 elara.config DEBUG Resources handed to GetTransitSchedulePath = {}
Traceback (most recent call last):
File "/usr/local/bin/elara", line 33, in <module>
sys.exit(load_entry_point('elara', 'console_scripts', 'elara')())
File "/usr/local/lib/python3.8/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/usr/local/lib/python3.8/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/usr/local/lib/python3.8/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/usr/local/lib/python3.8/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/usr/local/lib/python3.8/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/elara/main.py", line 64, in run
main(config=config, dry_run=dry)
File "/elara/main.py", line 79, in main
factory.build(requirements)
File "/elara/factory.py", line 735, in build
return build_dag(queue=queue, write_path=write_path)
File "/elara/factory.py", line 792, in build_dag
current.build(write_path=write_path)
File "/elara/factory.py", line 507, in build
tool.build(self.supplier_resources, write_path)
File "/elara/config.py", line 555, in build
self.path = self.config.transit_schedule_path
File "/elara/config.py", line 226, in transit_schedule_path
self.settings["inputs"]["transit_schedule"], "transit_schedule"
KeyError: 'transit_schedule'

Config:

[scenario]
name = "blah"
time_periods = 24
scale_factor = 1
crs = "EPSG:blah"
verbose = true
version = 12
using_experienced_plans = 'False'

[inputs]
events = "./output_events.xml.gz"
network = "./output_network.xml.gz"
plans= "./output_plans.xml.gz"
output_config_path = "./output_config.xml"

[outputs]
path = "./elara"
contract = false

[event_handlers]
link_vehicle_counts = ["car", "bike"]
link_vehicle_speeds = ["car", "bike"]
vehicle_link_log = ["all"]

[plan_handlers]
trip_modes = ["all"]
plan_modes = ["all"]
plan_logs = ["all"]
agent_highway_distance_logs = ["car"]
trip_highway_distance_logs = ["car"]

[post_processors]
vkt = ["car", "bike"]