Put dependencies and their versions into one place.

Support library modules were hardcoding versions of each library
each each build.gradle file. This change moves all these to
buildSrc/dependencies.gradle so we can update the version in the
future with a single file change.

Test: ./gradlew clean assemble assembleAndroidTest still works.
Change-Id: I4238c1182c095ae80d1d6dbb751f71c0ddfe191f

• build.gradle[diff]
• buildSrc/build.gradle[diff]
• buildSrc/dependencies.gradle[Added - diff]
• compat/build.gradle[diff]
• core-ui/build.gradle[diff]
• core-utils/build.gradle[diff]
• customtabs/build.gradle[diff]
• design/build.gradle[diff]
• fragment/build.gradle[diff]
• graphics/drawable/animated/build.gradle[diff]
• graphics/drawable/static/build.gradle[diff]
• media-compat/build.gradle[diff]
• percent/build.gradle[diff]
• transition/build.gradle[diff]
• v13/build.gradle[diff]
• v17/leanback/build.gradle[diff]
• v7/appcompat/build.gradle[diff]
• v7/gridlayout/build.gradle[diff]
• v7/mediarouter/build.gradle[diff]
• v7/palette/build.gradle[diff]
• v7/preference/build.gradle[diff]
• v7/recyclerview/build.gradle[diff]
• wearable/build.gradle[diff]