Cleanup
First steps of implementation

This commit provides a new architecture that is simpler
and might provide better performances. Instead of running
everything in threads, the network part is handle in the
main loop (but could be handled in another loop) while
all the heavy work (parsing information, creating models)
is done in worker threads, managed by a threadpool.
Refactoring and added loaders

More loaders were adapted to the new architecture.
Loaders, models and utilities are also migrated to
a spearated library, because these classes might
benefit for more users.
Added preprocessing system

This commit adds a preprocessing system that allows
the graph and arguments to be changed, as well as
fetching data in a cache, for example.

It also provides adapted picture loading system.
Restore feature parity

This commit restore feature parity with master, providing the missing
parts, that are getting feeds and images.
Cleanup
Fix compilation error
Cleanup

This commit cleans the huge enumeration that were used to
be keys for data from Facebook. Now, data is stored by
simply using the keys that are used inside facebook. They
are stored as constants and scattered into private headers.