[REBUILD] Allow disabling the confirm navigation popup

(cherry picked from commit 4f8ae7293230bca9a7a29fa3dc828a40532ef263)

Conflicts:
	manager/assets/modext/widgets/resource/modx.panel.resource.js
Improved "prevent navigation" alert by tracking field changes instead of using flawed isDirty() check.

The FormPanel.isDirty() check does a raw comparison between the original value and the current value of each of the fields. When using a rich text editor, there could be changes in the current content value of a resource due to changes in formatting (editors forcing a <p> root block) or encoding (& being turned into &amp;) which would result in the navigation popup. While yes, there are changes, no, the user did not make them so they should not be bothered with a popup.

The commit changes from looking at FormPanel.isDirty() to tracking field changes through the changeField event and a local flag.

This commit also resolves an issue where changing templates would show the warning during the reload.

(cherry picked from commit 5f24bb7fa025e4ae9c07d903e13d1c53b0c2fd41)

Conflicts:
	manager/assets/modext/widgets/resource/modx.panel.resource.js
Do not trigger confirmation dialog when the empty cache checkbox was triggered
Affects CacheMaster users.

(cherry picked from commit 7e95477189787071f11f9a7c2a06969df6b76b90)
add changelog entry
Improve Confirm Navigation feature and make configurable

Merge branch 'pr/820' into develop

* pr/820:
  add changelog entry
  Do not trigger confirmation dialog when the empty cache checkbox was triggered Affects CacheMaster users.
  Improved "prevent navigation" alert by tracking field changes instead of using flawed isDirty() check.
  [REBUILD] Allow disabling the confirm navigation popup