Convert the sequencers to the new 3.0 API

Now that we have a new sequencer API (see MODE-1310), we need to convert the existing sequencers. Most (if not all) of the sequencers use some internal or third-party component for parsing the content being sequenced, and then generate the derived content using the graph API. Only the latter part will need to be changed.

We should think about what kind of unit tests we want to support. Currently, most of the sequencer modules have true unit tests that do not actually use the graph API, but some modules do have some JUnit tests that set up a connector and use the graph API to verify the sequencer produced the right content. Since the sequencer API now uses JCR, we might want to provide a really good base class in the tests area of 'modeshape-unit-test' that sequencer modules can extend, allowing them to easily define tests that upload a specified file, wait for the sequencer to run, and verify the output of the sequencer. I'll log that as a separate subtask (if it's not needed, simply close).

This is a top-level task under which we'll create subtasks for each sequencer. It does not matter which order the sequencers are converted (though maybe a simple one like 'text' or 'image' or 'mp3' might be easiest to start out).

Note that this top-level task and all subtasks are targeted to 3.0.0.Alpha1. If any don't fit into that timeframe, we can easily retarget to Alpha2 or even Beta1 (at the latest).