Fixed noexcept on operator=nullptr_t

The assign operator for nullptr_t objects is
now noexcept if the deleter call operator is
noexcept. Also renamed reset() to Reset() to
be more in line with the naming conventions.
Added core.hpp

This header will include all the other
headers from the core subsystem.
Added ftxx::cContext class

This is the first draft for the FreeType2
Context class. Everything that has to do with
FreeType2 will now be managed with this class.
Renamed context_t to old_context_t

Renamed CreateContext() to CreateContextOld()
Added ftxx::CreateContext() method

This functions creates a unique_ptr of
ftxx::cContext. If you somehow need the
type then see ftxx::context_t.
Moved methods to ftxx::old namespace

Following methods and types have been moved
to the ftxx::old namespace and should not
be used anymore:

library_t
face_t
sLibraryDeleter
old_context_t
sFaceDeleter
font_t
E_RENDER_MODE
E_ENCODING
GetLastError()
ConvertFromRenderMode()
ConvertToRenderMode()
ConvertFromEncoding()
ConvertToEncoding()
CreateContextOld()
CreateFontFromFile()
CreateFontFromMemeory()
SetCharacterSizeInPoints()
SetCharacterSizeInPixels()
GetCharacterIndex()
LoadGlyph()
RenderGlyph()
SelectCharmap()

internals:
g_lastError