Build tasks produce errors if Growl/Snarl/notify-send is not installed

[bjagg]

Describe the bug
Building on a computer with OSX/Windows/Ubuntu triggers errors if Growl/Snarl/notify-send is not installed for the Gradle build-announcements plugin to use.

To Reproduce
Steps to reproduce the behavior:

1. Run ./gradlew clean portalInit on a computer without the above software

Expected behavior
No errors from build-announcements when above software is not installed

Platform:

• uPortal Version: uPortal 5
• OS: Windows 10, MacOS, Ubuntu

Additional context
Consider using gradle.properties and conditional plugin loading with a default of disabled to address this issue.
See:
https://docs.gradle.org/current/userguide/announce_plugin.html#announce_plugin
https://stackoverflow.com/questions/36039793/android-gradle-conditionally-apply-plugin-based-on-build-type

[bjagg]

This should also be addressed if present in uPortal, Notifications Portlet, and any other Gradle project.

N.B. This plugin is deprecated, so the simple solution is to remove it.