Loader: Implemented AppLoader interface for abstracting application loading.

- Various cleanups/refactorings to Loader, ELF, and NCCH modules.
- Added AppLoader interface to ELF and NCCH.
- Updated Qt/GLFW frontends to check AppLoader ResultStatus.

NCCH: Removed extra qualification typos.

Loader: Removed unnecessary #include's.

NCCH: Improved readability of memcmp statements.

NCCH: Added missing space.

Elf: Removed unnecessary usage of unique_ptr.

Loader: Removed unnecessary usage of unique_ptr.