leancloud-sdk-7.2.0

Break changes

• AVUser#currentUser doesn't work in lean-engine.
  AVUser#currentUser is a short-cut for use, only working within single thread, so it is not appropriate in lean engine.
  We disable AVUser#currentUser at present, and add many new methods for supporting requests with particular user authentication:

AVObject#saveInBackground(AVUser asAuthenticatedUser);
AVQuery#findInBackground(AVUser asAuthenticatedUser);

All these methods should be invoked in lean engine.

New features

• AVUser#becomeWithSessionToken(String sessionToken, boolean saveToCurrentUser) was added to change currentUser automatically.

Optimization and fixed bugs

• None