handle boolean flag for pbs files

[mathieudpnt]

The current job class does not handle boolean flag for pbs files, i.e. if one parse a boolean argument to a job instance, the value is treated as a string

script_arg = {arg_bool: False}

will write

--arg_bool False

However to parse booleans argument, one must respct the following convention:

--arg_bool

if set to True, else:

--no-arg_bool

I have added a private Job method to build the string representation of listed arguments that handles boolean values: _build_arg_string

[Gautzilla]

I like that, thanks!

I might tweak some lines in the osekit.public_api.dataset module to take this into account before merging but LGTM otherwise

[mathieudpnt]

[Gautzilla]