Use the docsJarFile setting in the play docs plugin
Use external project refs in documentation project
Throw meaningful error when form.get is called with errors

Fixes #1658

When a form is bound with missing fields, it throws an unhelpful
IllegalStateException with the message "No value".  Now it will instead
report the errors in the exception.
Added test for throwing an exception from Form.get
Fix deprecation version of JsResult.filter*
Fix JSON macro's support for case classes with a single custom generic field.

Prior to this, a compile-time error would be thrown when trying to create a formatter
for a case class with a single field that is of a custom type-parameterised type.

This change fixes that and simplifies some of the logic when trying to get unapplyTypes.
Merge pull request #3538 from pvlugter/doc-project-refs

Use external project refs in documentation project
Merge pull request #3491 from lloydmeta/feature/json-format-more-generic

Fix Json macro when passed case classes with a single custom generic field
Removed cloudbees from documentation
Merge pull request #3539 from jroper/1658-form-get-error

Throw meaningful error when form.get is called with errors
Merge pull request #3541 from jroper/remove-cloudbees

Removed cloudbees from documentation