added software processes

add schema
behavioral model
simulations
error classes

Working session APP/SD

big reorganization agreed during 2017-10-26

SCADE Model for function F_MM
 - completed for viability checks before take off
not completed for flight aspects

Root type System.Dim.Mks is of type Long_Long_Float which is not
supported in SPARK, on systems where this is a larger type than the
IEEE-754 64bits floats. Redefine a local version of Mks package to
use Long_Float as a root type instead.

Some units in types.ads are defined as floating-point types and others
as signed integer types. Start using the dimension system in GNAT on
floating-point units. Next step is to see if there is a benefit in using
floating-point types instead of signed integer types for the input and
output types, so that we can use the standard dimension system. Otherwise,
we could use a signed integer type with the Dimension_System aspect as
the root type for all these signed integer types.

Description of the architecture at multi-system level (layer 0).
Description of the incremental approach to architecture development.
Fail-safe design rationale, considerations on fault tolerance and development assurance.

Fix typos