Added decorator requirements_check for reducing code duplication

[itsdivyanshjain]

Checklist

• I have followed the Contributor Guidelines.
• The code has been thoroughly tested in my local development environment with flake8 and pylint.
• The code is both Python 2 and Python 3 compatible.
• The code follows the PEP8 styling guidelines with 4 spaces indentation.
• This Pull Request relates to only one issue or only one feature
• I have referenced the corresponding issue number in my commit message
• My branch is up-to-date with the Upstream master branch.

Changes proposed in this pull request

following code is been used in every start function of the module which leads to Duplication of code

      if target_type(target) != 'SINGLE_IPv4' or target_type(target) != 'DOMAIN' or target_type(target) != 'HTTP':
              # requirements check
              new_extra_requirements = extra_requirements_dict()
              if methods_args is not None:
                  for extra_requirement in extra_requirements_dict():
                      if extra_requirement in methods_args:
                          new_extra_requirements[
                              extra_requirement] = methods_args[extra_requirement]
              extra_requirements = new_extra_requirements

              #optional
              if target_type(target) == 'HTTP':
                  target = target_to_host(target)

             .
             #main code
             .
      else:
              warn(messages(language, "input_target_error").format(
                  'module_name', target))

we can use decorators e.g: @requirements_check(target_to_host=True,scan_name='xss_vuln') for that and
Also we can use socks proxy decorator as per #187.

Your development environment

• OS: Backbox
• OS Version: 7.1
• Python Version: 3.8.5 and 2.7.17

[Ali-Razmjoo]

fixed in #440