New option to keep event receiver when a new URL is loaded on webview

# Feature Request
New option to keep event receiver when a new URL is loaded on webview

## Motivation Behind Feature
If you load a different URL on Cordova Webview, the onPause() and onDestroy() methods of NetworkManager are called in PluginManager.init() and the event receiver is removed . The event listener is not recovered with onResume() as the plugin has not the 'onload' flag set to true (if you force it on config.xml the notifications still do not work).
This behavior is problematic if your application loads several URLs during its life-cycle.

## Feature Description
A new option to customize this behavior.

## Alternatives or Workarounds
I found no workarounds without changing the plugi's source code.

Start at PluginManager.init() and trace NetworkManager.onPause(), onDestroy(), and onResume() when a Cordova Webview loads a new URL. Review how the onload option in config.xml affects this lifecycle, then define and test an option that preserves the event receiver and restores notifications across URL loads.

Written by the indexing model from the issue text.