Adds onAttach triggerMethod.

Adds `triggerAttach` and `beforeTriggerAttach` triggerMethods.

This is the 3rd out of 3 PRs to get #1886 in.
So for everyone like me who was thinking. 700 lines of tests, good god what has jmeas done - here's a short summary
---

#### when showing a region that is not attached to the document
	should not call either trigger method on the view ‣
#### when showing a region that is attached to the document
	should call onBeforeAttach on the view ‣
	should call onAttach on the view ‣
#### when showing a region that is attached to the document & has triggerBeforeAttach set to false
	should not call onBeforeAttach on the view ‣
	should call onBeforeAttach on the view ‣
#### when showing a region that is attached to the document & has triggerBeforeAttach set to false, but the option is passed as true
	should call onBeforeAttach on the view ‣
	should call onAttach on the view ‣
#### when showing a region that is attached to the document & has triggerAttach set to false
	should call onBeforeAttach on the view ‣
	should not call onAttach on the view ‣
#### when showing a region that is attached to the document & has triggerAttach set to false, but the option is passed as true
	should call onBeforeAttach on the view ‣
	should call onAttach on the view ‣
#### when a view is shown in a region
	should be detached in onBeforeAttach ‣
	should be attached in onAttach ‣
#### when the parent view is initially detached
#### When showing a View in a Region
	should trigger onAttach on the View a single time ‣
	should trigger onBeforeAttach on the View a single time ‣
	should trigger onBeforeAttach before onAttach ‣
#### When showing a LayoutView with a single level of nested views that are attached within onBeforeShow
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the footerView a single time ‣
#### When showing a LayoutView with a single level of nested views that are attached within onBeforeAttach
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onAttach on the mainView a single time, but not onBeforeAttach ‣
	should trigger onAttach on the footerView a single time, but not onBeforeAttach ‣
#### When showing a LayoutView with two levels of nested views; with onBeforeShow for the first and second level
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the headerView a single time ‣
#### When showing a LayoutView with two levels of nested views; onBeforeShow for the first level, then onShow for the second
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the headerView a single time ‣
#### When showing a LayoutView with two levels of nested views; with onShow for the first level, onBeforeShow for the second
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the headerView a single time ‣
#### When showing a LayoutView with a single level of nested views that are attached within onShow
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the footerView a single time ‣
#### when the parent view is initially attached
#### When showing a View in a Region
	should trigger onBeforeAttach & onAttach on the View a single time ‣
#### When showing a LayoutView with a single level of nested views that are attached within onBeforeShow
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView twice ‣
	should trigger onBeforeAttach & onAttach on the footerView twice ‣
#### When showing a LayoutView with two levels of nested views; with onBeforeShow for the first and second level
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView twice ‣
	should trigger onBeforeAttach & onAttach on the headerView twice ‣
#### When showing a LayoutView with two levels of nested views; onBeforeShow for the first level, then onShow for the second
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView twice ‣
	should trigger onBeforeAttach & onAttach on the headerView twice ‣
#### When showing a LayoutView with two levels of nested views; with onShow for the first level, onBeforeShow for the second
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the headerView a single time ‣
#### When showing a LayoutView with a single level of nested views that are attached within onShow
	should trigger onBeforeAttach & onAttach on the layoutView a single time ‣
	should trigger onBeforeAttach & onAttach on the mainView a single time ‣
	should trigger onBeforeAttach & onAttach on the footerView a single time ‣