[Application] [Extension] Added two permission APIs.

CheckAPIAccessControl
This API is for external extension developer. The API need to be called in the
implementation of each exported API in C or C++ code. For C extension
implantation, header file "public/XW_Extension_Permissions.h" should be
included. For each API that need access sensitive data, developer should call
CheckAPIAccessControl for API control. For C++ extension implantation, header
file "xwalk/common/xwalk_external_extension.h" should be included.

RegisterPermissions
The runtime permission mapping is registered by extension which
implements some specific API, for example: "bluetooth" ->
"bluetooth.read, bluetooth.write, bluetooth.management" Whenever there
comes a API permission request, we can tell whether this API is
registered, if yes, return the according permission name.