Context arguments handling refactoring

[everzet]

• Moved context class arguments setup back under the suite settings
• Extracted context creation logic into ContextFactory
• Added support for named context arguments

Basically, this PR adds full and equal support for next three setups:

default:
  suites:
    project:
      contexts:
        - VisitorContext
        - AdministratorContext

default:
  suites:
    cli:
      contexts:
        - CronContext:
            - 24
            - 13
            - 72
        - APIContext

default:
  suites:
    web:
      contexts:
        - VisitorContext
        - MinkContext:
            baseUrl: 'http://localhost'

Arguments will be passed to context classes separately (each value under the behat.yml context definition will become separate context argument). No more nonsense with array $parameters. Time to make our contexts POPO once again :)

[stof]

shouldn't it be removed ?

[everzet]

@stof fixed. Thanks!

[everzet]

@stof what do you think about it? Mergeable?