feat!(3.0.0): bump to 3.0.0 w/ Android Phase 1 Updates

[erisu]

Description

Merge in 3.0.0 changes

Related Issue

resolves: #114

Motivation and Context

• Drop Android Support Library
• Use AndroidX Library
• Update libraries and dependencies
• Use Latest Google Services Gradle Plugin

How Has This Been Tested?

• Create Cordova Project
• Add Plugin to Cordova Project
• Build App
• Ran App
• Send Sample Push Notification Test from Firebase Cloud Messaging Console

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[erisu]

• All commits were separated into their own PRs and merged.
• The AndroidX commits were grouped under 1 PR.

As the PRs were already merged into master, this PR will be closed as resolved without merge.
This PR is only for context, and used testing all changes together.

The doc PR #122 will be merged in at a later time.