SDK: Javadoc since tags

[pavolloffay]

Related to #342 (comment)

In the API all public APIs are documented with @since javadocs.

Should we do the same in SDK? For the interfaces it does not makes much sense as the since tag is in the API and SDK will have the same version.

[yurishkuro]

We should, but maybe we should defer that until we have a stable API?

[JasonXZLiu]

Hi! Is this issue free to pick up? I would love to work on it for a good first issue! cc - @alolita

[jkwatson]

@JasonXZLiu Sure thing. I'll assign it to you.

[SaberSeddik]

Was checking for good first issue, found this. But seems a fix already merged. should this be closed ?

[jkwatson]

I think we'll want all of the @since tags to be set to 1.0.0, but not until we're ready for a release candidate (which is hopefully coming soon!). So, I think this should be open until then.

[anuraaga]

We discussed adding @since tags for post-1.0 versions.

[jkwatson]

I think we can close this. We'll add @since tags on new APIs/methods that we add, and if it becomes important, we can retro-fit the @since tags on existing APIs.