Draft for libGDX Pay API.
Purchase object improved to accept both an integer or String in the constructor for the item identifier.
Merge branch 'master' of https://github.com/noblemaster/libgdx into iap
added gdx-pay to build
Merge branch 'master' of https://github.com/libgdx/libgdx
Merge branch 'iap' of https://github.com/libgdx/libgdx
Pay API:
 - removed PurchaseObserver - there is now only 1 single listener: PurchaseListener
 - itentifier changed to String (from int).
Merge branch 'iap' of https://github.com/libgdx/libgdx
Added payment processor stubs for Google Wallet/GWT and Stripe/Desktop.
Fix TextureUnpacker
GWT
Typo
Add support for DELETE and PUT

Closes #1985
add setCenterPosition and other methods to Actor
Merge pull request #2000 from jrenner/actor-centerpos

add setCenterPosition and other methods to Actor
Merge branch 'master' of https://github.com/libgdx/libgdx
Merge pull request #2002 from alex55i/unpackerfix

Fix TextureUnpacker
some scene2d ui docs
Merge pull request #2003 from jrenner/docs

some scene2d ui docs
Merge branch 'master' into p3d

Conflicts:
	gdx/src/com/badlogic/gdx/math/Matrix4.java