New method `toTask` on `Initialize[InputTask[T]]` to apply the full input and get a plain task out.
Filter test options are backwards

The itFilter, defined as integration tests are configured to be run under task 'test' where I think you meant to hav then run under 'fun:test' and vise versa for the unitFilter.
Change how test labels are combined, per code review comments.
Merge remote-tracking branch 'benjy/analysis_test2' into 0.13
Process settings once in SettingGraph for better performance.

Running 'inspect tree sbt/update' on sbt goes from 27 s to <1 s.
Review by @eed3si9n.
updated links for my plugins that moved to the sbt org on github, added testng plugin
Docs: fix taskKey usage in Custom Settings example

Following commentary on 126f41c0ac1
drop view for iterator in IMap
cleanups in Settings
shortcut heterogeneous AList to KList.toList
Better representation of no cross-version suffix in suffix conflict error message.
Remove AnalysisCallback.{beginSource, endSource} methods.

As pointed out by @harrah in #705, both beginSource and endSource are
not used in sbt internally for anything meaningful.

We've discussed an option of deprecating those methods but since they
are not doing anything meaningful Mark prefers to have compile-time
error in case somebody implements or calls those methods. I agree with
that hence removal.
Move dependency extraction into separate compiler phase.

This is the first step towards using new mechanism for dependency
extraction that is based on tree walking.

We need dependency extraction in separate phase because the code
walking trees should run before refchecks whereas analyzer phase runs
at the very end of phase pipeline.

This change also includes a work-around for phase ordering issue with
continuations plugin. See included comment and SI-7217 for details.
Add a bit documentation to Dependency phase.

It gives some high-level overview of what this phase does.
Remove long comment that explains phase ordering issues.

As pointed out by @harrah in #705, we might want to merge both API
and dependency phases so we should mention that in the comment explaining
phase ordering constraints instead.

I'd still like to keep the old comment in the history (as separate commit)
because it took me a while to figure out cryptic issues related to
continuations plugin so it's valuable to keep the explanation around in
case somebody else in the future tries to mess around with dependencies
defined by sbt.