GitLab

* Added scaffolding for external programmer support

* Added programmers extraction in arduino/cores module

* Implemented programmers list command

* Print upload command line in verbose mode

* Added programmer option to compile command

* External programmer implementation

* Factored function runTool in upload

This will turn out useful for burn-bootloader that requires to run
two actions in a row ("erase" and "bootloader").

* Implemented burn-bootloader

* Increased tracing log

* Test fix

* Added BurnBootloder action

* Make the upload port parameter mandatory only when really needed

* Fixed nil pointer exception when burning-bootloader

* Added sanity check on upload parameters