Doc: Bring groovy versions back into alignment

Minor change to userguide to bring groovy versions back into alignment.
Documentation fix: your are -> you are
GRADLE-2171: Added DuplicatesStrategy allowing duplicate
files (based on their path) to be included or excluded, by
default for an entire copy operation or on a per-file basis

- duplicatesStrategy field to FileCopyDetails so individual files
  can specify their own strategy for handling duplicates

- add duplicatesStrategy field to CopySpec so that an entire copy
  spec can specify the default strategy (this can be overridden
  for some or all files)

- add CopySpec.matching and .notMatching convenience
  methods. These let the user modify a group of FileCopyDetails
  simultaneously. Motivated by setting a duplicatesStrategy for
  eg, "META-INF/**/*.xml" but is generally useful

- added CopySpec.duplicatesPriority that determines precedence
  among CopySpecs when a duplicate file is to be
  excluded. Plugins can set a higher duplicatesPriority for some
  specs (eg, Jar.manifest and Jar.metaInf), but this property is
  not currently user-settable.
GRADLE-2171 Improve documentation for DuplicatesStrategy-related method calls and add to DSL documentation
Added support for bintray's jcenter repository
Merge from master
GRADLE-2171 Restore imports lost while merging conflicts
GRADLE-2171 Change case of DuplicatesStrategy enumeration so that Gradle can automatically coerce strings to enum types.
GRADLE-2171 Remove duplicate priority logic, expect specifications to be ordered based on their precedence. Right now the Ear test for deploymentDescriptor precedence is failing
Merge branch 'master' of https://github.com/gradle/gradle
Integration test for jcenter resolution
Added a description for jcenter resolution and a minimal background about jcenter
GRADLE-2171 Remove DuplicatesStrategy.INHERIT which will just be represented by null
fix gradle-wrapper ignoring -g / --gradle-user-home switches
Update bndlib to the latest 2.1.0 version
Added some stuff to the gradle-2.0 spec
GRADLEREV-1 - Mention contribution in release notes
Fix whitespace in build setup templates.
whitespace and formatting
Introduce constants for the build setup type ids.