Connected to #2855

Method initialize in FMUModelCS2 has correct order of the input arguments.
Also the handling of relative tolerance inside the method is safer

Connected to #2855
Related to ticket: #2785 and #2856

-- The method get_capability_flags() in FMUModelBase2 now returns capabilities
according to instantiation (ME or CS)

-- Checking that the object returned when parsing the XML-file is not a NULL-pointer. This occurs in load_fmu2 and __init__() in FMUModelBase2

Related to ticket: #2785 and #2856
Fixed a crash when simulating a model without any states and time-events that indicates (wrongly) that the state value references has changed. Related to ticket:2862