Add support for mynewt

[danielkucera]

I'd like to see mynewt supported in platformio.
I was using mbed but it is removing support for more and more boards and zephyr still doesn't have the features mynewt has.

https://mynewt.apache.org/

[affanse]

This should be easy original link

Install:

git clone https://github.com/apache/mynewt-newt
cd mynewt-newt/
./build.sh 
mv newt/newt ~/.local/bin/

Build Ble App:

cd ~
mkdir Projects && cd $_
newt new my_proj1
newt upgrade
newt pkg new apps/ble_app -t app
newt target create ble_tgt
newt target set ble_tgt app=apps/ble_app bsp=@apache-mynewt-core/hw/bsp/nordic_pca10056 build_profile=optimized
vim apps/ble_app/pkg.yml
    ......
    - "@apache-mynewt-core/sys/stats/full"
    - "@apache-mynewt-nimble/nimble/host"
    - "@apache-mynewt-nimble/nimble/host/store/config"
    - "@apache-mynewt-nimble/nimble/transport"

vim apps/ble_app/src/main.c
.....
#include "host/ble_hs.h"
.....

newt build ble_tgt

Upload (attach first):
newt run ble_tgt 0