libragephoto: add C++ namespaces (API change)

- RagePhoto::saveFile() -> use const char* instead of std::string
- RagePhoto C++ -> C API: try catch for throwable functions (to match C
impl. behaviour)
- Rename header files and classes

doc/index.doc

@@ -12,8 +12,8 @@
 \subpage Usage "Using libragephoto"
 
 <b>Reference</b>  
-RagePhoto (C++ API)  
-RagePhotoA (C++ API based on C API)  
+ragephoto::cxx_abi::photo (C++ API)  
+ragephoto::c_abi::photo (C++ API based on C API)  
 RagePhoto.h (C API)  
 RagePhotoData (Data Object Struct)  
 RagePhotoFormatParser (Custom Format Parser Struct)

doc/usage.doc

@@ -4,7 +4,7 @@
 
 <h4 id="cxx_include_usage">Including and using RagePhoto</h4>
 
-Include RagePhoto (C++ native), RagePhotoA (C API wrapper) or \link RagePhotoB.hpp RagePhotoB \endlink (best implementation)
+Include RagePhoto
 
 \code{.cpp}
 #include <RagePhoto>