Integration Candidate: 2020-05-27

Integration Candidate: 2020-06-10

Integration Candidate: 2020-06-17

Add more hooks for additional flexibility when adding
modular code blobs into the build.

Three new directives are added:

MISSION_CORE_MODULES, for modular components which are
direct dependencies of CFE core and/or extend its functionality.

MISSION_GLOBAL_APPLIST, for applications/libraries which
should be built for every target, as if they were listed
in every TGTx_APPLIST setting.

MISSION_GLOBAL_STATIC_APPLIST, same as above but for the
TGTx_STATIC_APPLIST setting.

This also simplifies/reworks the search path to remove
some logic that was never really utilized.

The existing build system built target executables grouped by toolchain
as a proxy for CPU architecture + machine options/flags.  The app binaries
would be built once and copied to any/all targets sharing that toolchain.

The side effect of doing this is that the application needs to be written
in an CPU-agnostic manner, performing its subscriptions and configurations
from runtime table data rather than hardcoded/fixed values.  Unfortunately
most apps are not coded that way, so workarounds were needed.

This changes the top level process to include the "platform" within this
target build logic, effectively treating different platform configs as
entirely different builds, even if they share the same toolchain file.

As a result, binaries will only be shared between targets that explicitly
set the "TGTx_PLATFORM" setting in targets.cmake to the same value.

Put more dependencies into the "mission_defaults.cmake" file for
more visibility and ease of configuration.  This now includes all
"implicit" modules such as cfe-core, osal, and psp.

Also push the calls to "generate_config_includefile" to a sub-script
which can be distributed with each app and evaluated as part of the
build.  This reduces dependencies on special naming conventions like
"fsw/mission_inc" and "fsw/platform_inc", and apps can explicitly manage
the files that users are expected to override.