fbt: initial blackmagic support (#1362)

* fbt: added separate script for Windows env setup; moved flash targets from firmware.scons to SConstruct; added Blackmagic support with automatic probe port resolution; added apps.c rebuild on any manifest.fam changes; fixed simultaneous flash & debug ops
* fbt: added networked BlackmagicResolver mode; added `get_blackmagic` target for IDE integration
* fbt: cleanup
* fbt: docs update; fixed blackmagic lookup on certain usb hubs
* fbt: removed explicit python serial port import
* fbt: cleanup
* fbt: raising exception on multiple serial blackmagic probes

fbt

@@ -6,7 +6,6 @@ SCRIPTDIR="$( dirname -- "$0"; )";
 SCONS_EP=${SCRIPTDIR}/lib/scons/scripts/scons.py
 
 if [[ -d .git ]]; then
-    echo Updating git submodules
     git submodule update --init
 else # Not in a git repo
     echo Not in a git repo, please clone with git clone --recursive