add find and replace feature to force_post

[dunderhay]

Add the ability to find and replace a value inside the force_post key-pair.

This would work in the following way:

First, look for a key-value pair in the POST request body. If a match is found, then look for a particular string pattern inside the value of the key-pair. If the search string is found inside the value, replace only the part of the data that matches - otherwise operate as normal and replace the entire key-value pair.

Hopefully that makes sense. Let me know if any clarification is needed.

Documentation that needs to be updated:

force_post:
  - path: '/sessions'
    search:
      - {key: 'session\[user.*\]', search: '.*'}
      - {key: 'session\[pass[a-z]{4}\]', search: '.*'}
    force:
      - {key: 'remember_me', search: '.*', value: '1'}
    type: 'post'

• path (regexp): Regular expression to match the URL path the intercepted POST request will be sent to.
• search: Trigger POST arguments. ALL of the defined here POST arguments must be present in the POST request, for the POST arguments to be inserted or replaced.
• key (regexp): Regular expression to match the POST argument key.
• search (regexp): Regular expression to match the POST argument value.
• force: List of POST arguments to insert or replace in intercepted POST request.
• key (string): Name of the POST argument.
• search (regexp): Regular expression to match the value inside the specified key.
• value (string): Value of the POST argument.
• type (string): Type of the POST request to handle. Currently only post is supported.