Implement "Step" design for Flash process

Description

Add a new structure for config file, a new way to parse them and a new way to use it in Easy-installer. It will be easier to understand and to maintain; It will also include unit tests

Issue(s)

Closes #361

Test environment

• non regression test

/!\ Checked OS should at least be tested: /!\

• windows
• linux
• MacOS Not supported yet_

/!\ Checked devices should at least be tested: /!
If no device checked, then you can pick anyone from the list

• GS290
• FP3
• 2e
• starlte
• star2lte
• dreamlte
• dream2lte
• herolte
• hero2lte

HOW TO SETUP

• Download build from latest pipeline of this MR

windows

• Extracted Installer from the build downloaded
• Double click on it
• Follow the setup wizard
• Start from shorcut in menu

linux with Snap

• You need to have snap available from your shell.

  • Debian/ubuntu based :

    sudo apt install snapd

  • Fedora based :

    sudo dnf install snapd

  • Arch linux based :

    yaourt -S snapd
    sudo systemctl enable --now snapd.socket

• Extract snap file to some location

• Open shell prompt and move to this location (using cd )

• run : sudo snap install --dangerous <yourFile.snap>. Note: I have a doubt about sudo

• run : snap connect easy-installer:adb-support

• run : sudo snap connect easy-installer:raw-usb

Uninstall the easy-installer test build:

Windows:

• Open menu
• Right click on easy-installer
• select uninstall

Or remove it like any other software from uninstall settings menu.

Linux:

• run sudo snap remove easy-installer in a shell

Test procedures

• Run the easy-installer
• Flash a device

The same behaviour and UI is expected as in the latest official released version

/!\ As it changes config files for every device, every device must be tested /!\

/!\ It's not mandatory to flash each device on both windows & linux. Only one is enough with windows. So we could split the above list in devices to flash with linux & devices to flash windows.

Check list

• Self review
• Test procedure explained
• Tested on fresh install
• Tested applied as an update
• License
• Internal documentation
• User documentation