Consider a shift to primarily intrinsic plug-ins that can be enabled/disabled

[dbenn]

As plugins become stable and mature, we could migrate them into the main codebase.

We already have some intrinsic plugins, e.g. AID and simple/AAVSO Download format, DCDFT, WWZ.

All plugins could still appear in the Plugin Manager but some would be part of the code base, so an installation would mean nothing more than a Preferences API update when Install/Delete button is clicked.

IPlugin may need a method such as isIntrinsic() that every plugin must implement.

All intrinsic plugins could be disabled and will need to be "installed" via the plug-in manager.

One benefit here is that any WebStart sensitive code will no longer be a problem if part of an intrinsic plugin. Note: no longer an issue since we don't support WebStart now.

Another will be speed of plugin installation which has admittedly never been very slow.

We don't tend to make new plugin releases until we release a new version of VStar anyway. However, we can still make plugin releases as remote plugins as all are now but they could be more experimental or meet demands without the need for as much stability.