feat: pre UI code

[m1ga]

Inside the generated controllers it looks like this:

  // Generated code that must be executed before all UI and/or
  // controller code. One example is all model and collection
  // declarations from markup.

  // Generated UI code

and after that it will add the code of the controller. Currently there is no way (unless someone knows one) to put controller code before creating all the UI code which e.g. calls createController and creates sub controllers already.
Only Backbone collections are before the UI code.

Alloy already provides a pre field for "pre code" stuff but it is not used.

This PR will add a way to use a method called __pre() to fill that property. So all you code inside function __pre(){} will be added before the // Generated UI code section.

Example:

• create an Alloy project
• create e.g. a TabGroup where you require the Tab from a different controller
• add a console.log("controller") in that controller
• add function __pre(){console.log("index");} into index.js

"index" should be logged before "controller"

Note
We can change the name of the method to something else like __alloy_preCode or so. Just to make it more unlikely to cause conflicts with existing function names.