GH-480 (android): Add option to open system's browser in a new task

[thomasletallec]

Platforms affected

Android

Motivation and Context

When opening external app with inAppBrowser using target: _system, sometimes we lose the ability to go back to the initial app, as described in #480

Closes #480
Closes #735

Description

This PR add an option launchInNewTask which, when used with target: _system on android, add the flag Intent.FLAG_ACTIVITY_NEW_TASK to the Intent used to launch system's browser.

Testing

I have an (proprietary) ionic/cordova app where I encountered this issue when opening geo: url with InAppBrowser.
I checked that the issue is still here when I don't add the new option launchInNewTask, and that this issue is gone when I add launchInNewTask=yes to the options.

I didn't add any new automated tests - not sure how.

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[ipunkvizard]

This issue is a blocker for me, and this pull request solves the problem.
Thank you.

InAppBrowser.open(url, '_system', 'launchInNewTask=yes')