Bump to our own nightly of ivy 2.4.0 (RC1+).

* Testing the infrastructure to use our own instance of ivy
* Allow us to push bug-fixes/performance directly into ivy
  on our own pace, as we submit patches back to ivy master
Bump ivy version to include exclusion performance fix.
Added TestResultLogger for customising test feedback.

1) When `test` is run and there are no tests available, omit logging output.
   Especially useful for aggregate modules. `test-only` et al unaffected. (#1185)

2) Added a new setting `testResultLogger` to allow customisation of logging of test results.
Fix infinite loop of death.
Merge pull request #1245 from sbt/fix/infinite-loop

Fix infinite loop of death.
Merge pull request #1225 from japgolly/shhh_tests

Added setting 'testResultLogger' which allows customisation of test reporting.
Relativizing CONTRIBUTING.md
`DefaultOptions` for resolvers should not resets existing values.

`DefaultOptions.addResolvers` and `DefaultOptions.addPluginResolvers`
should not reset the existing value while adding the new ones. The
names are prefixed with _add_ afterall.
`DefaultOptions` for resolvers should not resets existing values.

`DefaultOptions.addResolvers` and `DefaultOptions.addPluginResolvers`
should not reset the existing value while adding the new ones. The
names are prefixed with _add_ afterall.
Merge pull request #1249 from indrajitr/fix-default-options

`DefaultOptions` for resolvers should not resets existing values.
Merge pull request #1248 from indrajitr/0.13

Relativizing CONTRIBUTING.md
Pick the right overload in EvaluateTask.runTask

The deprecated method should forward to the other overloaded alternative
but it recursed instead.

This kind of mistake would be easily caught by linter warning about
unused `newConfig` local variable. I hope we'll get there some day.

Fixes #1251
Merge pull request #1252 from gkossakowski/hang-in-loading-global-plugins

Pick the right overload in EvaluateTask.runTask
Create test for configuration ordering regression.
Autoplugin confgiurations must be injected first into project.

Fixes #1247
Merge pull request #1226 from sbt/wip/bump-to-latest-ivy

Bump to our own release of ivy 2.4.x
Mark new method private[sbt] because no one else should use it.
Merge pull request #1253 from sbt/wip/fix-1247

FIx configuration ordering issues in sbt 0.13.5
Add some of the latest 0.13.5 changes to the doc.
Move NameHashing from incremental to api subproject.

It should have been there from the beginning because NameHashing is tied
to internals of the API subproject.

It was added to incremental subproject by mistake.