chore(ios,android): move samples out of keymanapp/keyman repository

I would like to move the sample projects out of the keymanapp/keyman repository into their own repos that are easily cloned by other developers. However, I don't want to lose the canary property of them, so I would like to also update our CI to continue to build them even when they are in a separate repo, ideally pulling in the binary Engine artifacts from the branch's most recent ios or android build, so that we can verify that the samples continue to work with new versions of Engine etc.

Then eventually they would also need their own CI builds to verify that they build with latest stable iOS/Android Engine.

This decoupling has the potential for versioning/dependency chaos so we need to take care with this.