List all extension points and extensions for a plugin

[decebals]

I think that it's nice to have a possibility to list all extension points and extensions that come with a plugin.
It's nice to have a kind of plugin's documentation created automatically.

[decebals]

We have already this information (see LegacyExtensionStorage), all we have to do is write this information in the extensions.idx file.

[decebals]

The first step in my opinion is to improve the format (content) of the extensions.idx file.
Now the format is very simple, with one extension id (class) on each line. As example I will present you the content of extensions.idx for the welcome plugin (see demo):

# Generated by PF4J
org.pf4j.demo.welcome.WelcomePlugin$WelcomeGreeting

My propose is to add also on the same line, the extension point(s) implemented by extension, separated by : as delimiter:

# Generated by PF4J
org.pf4j.demo.welcome.WelcomePlugin$WelcomeGreeting:org.pf4j.demo.api.Greeting

So, we have the extension (org.pf4j.demo.welcome.WelcomePlugin$WelcomeGreeting) and the extension point (org.pf4j.demo.api.Greeting) separated by : delimiter character.
The first big benefit is that we can avoid the reflection (time consuming) at runtime to discover the extension point(s) for an extension.
The second benefit is that we can create a nice documentation.

[decebals]

To list all the extension points defined by a plugin, I think that we need a separate (probably) storage extension-points.idx. The format of the new file can be identical with the actual format of the extensions.idx, with one extension point id (class) on each line.
Other idea is to put this information (with all extension points) in the already existed extensions.idx.