Plugin Template updates for 3.0

[imhoffd]

• class names are inconsistent between native and web "I entered MyPlugin and that created a plugin that's accessible via Capacitor.Plugins.MyPlugin"
• provide an initial separation between functionality and bridge communication (see Capacitor v3: Make plugins usable for native code #3222 and chore(cli): Add functionality class to plugin template #3315)
• implement a better example for a plugin https://github.com/ionic-team/capacitor/issues/3353
• verify that unit tests work
• change how the plugin is imported (see Plugin Import Proposal and Plugin Import updates #3305)
• remove extraneous xml files for Android (see chore(cli): remove example xml files from plugin template #3351)
• update min java version to 8 (see fix(cli): update plugin template to compile using java 8 #3350)
• update gradle (see chore: Update gradle tooling on plugin template #3310)
• investigate adding kotlin support
  • We are going to keep it Java for now and document how to add Kotlin to a Capacitor plugin. See Adding Kotlin to a Capacitor Plugin capacitor-site#77
• registerPlugin.getImplementation can provide a proxy fallback that logs warnings for unimplemented platforms (see fix(core): provide mock implementation for unimplemented platforms #3352)
• add fmt script (see feat(cli): add fmt script to plugin template #3354)

[jcesarmobile]

gradle should be updated to latest on android plugin template, see #3310

[carlpoole]

All 3 xml files in the values dir can be removed if desired, the template functions fine without them - (Tested).

[ionitron-bot]

Thanks for the issue! This issue is being locked to prevent comments that are not relevant to the original issue. If this is still an issue with the latest version of Capacitor, please create a new issue and ensure the template is fully filled out.