phpstan baseline generation

[SebSept]

provide a command to generate a baseline and add it the configuration file.

(Baseline collect errors, put them in a file, then, after including the generate file in the phpstan config, these errors are not displayed anymore).

[SebSept]

Note :

• include the baseline file requierement in the .php_cs.dist file
• create an empty baseline file
• add an option to psdt:phpstan --generate-baseline that write the baseline in the baseline file