Support portable folder workflow for local installation

[PradeepMW]

Similar to portable folder workflow in the main IDE, provide a similar option in the command line interface.

[cmaglie]

There are currently two way to achieve this.

1. Create your .cli-config.yml file with the following content:

sketchbook_path: /home/cmaglie/Workspace/sketchbook-cores-beta
arduino_data: /home/cmaglie/.arduino15

and set sketchbook_path and arduino_data to your preferred location.
You can check if the CLI is reading the config with the command:

$ arduino-cli config dump
proxy_type: auto
sketchbook_path: /home/cmaglie/Workspace/sketchbook-cores-beta
arduino_data: /home/cmaglie/.arduino15

(you can also add --debug if it's not taking your config file to see what's happening)

2. you can use the env variables ARDUINO_DATA_DIR and ARDUINO_SKETCHBOOK_DIR:

$ ARDUINO_DATA_DIR=~/arduino/data ARDUINO_SKETCHBOOK_DIR=~/arduino/sketch arduino-cli config dump
sketchbook_path: /home/cmaglie/arduino/sketch
arduino_data: /home/cmaglie/arduino/data

[masci]

I'm closing this, feel free to join the conversation here: #108