Major restructuring of magics, breaking them up into separate classes.

This is the first step to get the new magic architecture in place,
with a new base class for magic functions.

At this point IPython does *not* run, but the changes are extensive
enough to warrant intermediate non-working commits.

IPython/core/interactiveshell.py

@@ -380,6 +380,7 b' class InteractiveShell(SingletonConfigurable):'
     plugin_manager = Instance('IPython.core.plugin.PluginManager')
     payload_manager = Instance('IPython.core.payload.PayloadManager')
     history_manager = Instance('IPython.core.history.HistoryManager')
+    magics_manager = Instance('IPython.core.magic.MagicsManager')
 
     profile_dir = Instance('IPython.core.application.ProfileDir')
     @property