Improve opts parsing and passing config params from command line in submit

With this patch, the submit command will complain if any argument (not option) is not in the format <section>.<parameter-name>=<parameter-value>. Because arguments in the submit command are supposed to be all arguments to override config parameters. If the argument does not have an '=' sign and starts with '-' (it is a candidate to be an option, e.g. -w) it will suggest to put this argument right after crab submit. 
Also, the configuration file when passed as an argument (not using the -c option) then it doesn't have to be the first argument (this is probably too much flexibility...). I.e., this is allowed: $ crab submit -w Data.publication=False myconfig.py
It will recognize that the configuration file is myconfig.py, and Data.publication=False is a paremeter to override in the config.
If one specifies $ crab submit -w Data.publication=False myconfig.py myconfig2.py
it will complain that it can not unambiguously recognize the configuration file and it will tell that the candidates are ['myconfig.py','myconfig2.py'].