Hooks doc_events on a dynamic list of doctypes

Hi @guimorin,

Particular doctype doc_event method call for apply it like:

# Syntax
doc_events = {
  "Your DocType": {
      "on_update": "your_method_with_proper_path"
  }
}

# Example
doc_events = {
  "Lead": {
      "on_update": "method.testcall"
  }
}

Thank You!