Give up on Eclipse for Android; convert older projects to pure Gradle/AndroidStudio format

[IanDarwin]

At this point many of the examples need updates to their build.gradles etc. I will accept pull req's that remove the Eclipse files and optionally rearrange the project into "proper" (but wasted) "app/" structure. 99% of simple apps don't have more than one module, but Studio imposes an extra level of directory structure. But I'm tired of swimming against the current on that, so... full steam ahead for modularization, studification, etc.

Some projects are so out of date that they should probably be deleted.

This Issue won't be closed until all projects are converted, so please DO NOT cite it in your commits as that will cause GH to close this issue.

[TinaT2]

Please list the samples that still need to be updated.

[IanDarwin]

A lot of them were converted in commit 748ffd4. Many of these still have pom files, which can be deleted iff the project builds successfully under gradle, otherwise, the project needs work.
Also, EventListenersDemo needs to be reworked into modern form; there are probably a few others.
Also, a "master" gradle build that builds all the projects would be nice; if that isn't easy to do in Gradle, a simple shell script would do the job.