Change from "{}" to "()" initialization of JniClass<C>::s_initializer to fix compiler error on MSVC2013.
Prefix GlobalRefDeleter & LocalRefDeleter with djinni namespace when being used as unique_ptr deleter.

Work-around for MSVC2013 bug:
https://connect.microsoft.com/VisualStudio/feedback/details/781054
Add missing move constructor to GlobalRef.

Fixes compile error on MSVC2013.