This commits consists of three major changes:
1. Support a new interface to get the base64 quote only.
This is useful in the case that application sends the quote
to service provider server and get the final IAS report there.
The application itself doesn't depend on IAS in this case.
2. Improve the C++ programming style. Now, we only provide
C++ classes and limited C APIs(for configuration and sgx device).
3. Use the more general keywords as names prefix.
Signed-off-by: Junxian Xiao <junxian.xjx@antfin.com>
