[Docs] Update downloader framework docs (#914)

* Update installable

* Update Repo manager

docs/framework_downloader.rst

@@ -1,7 +1,45 @@
 .. downloader framework reference
 
-Downloader Framework Reference
-==============================
+Downloader Framework
+====================
+
+Info.json
+*********
+
+The info.json file may exist inside every package folder in the repo,
+it is optional however. This string describes the valid keys within
+an info file (and maybe how the Downloader cog uses them).
+
+KEYS (case sensitive):
+
+- ``author`` (list of strings) - list of names of authors of the cog
+
+- ``bot_version`` (list of integer) - Min version number of Red in the format ``(MAJOR, MINOR, PATCH)``
+
+- ``description`` (string) - A long description of the cog that appears when a user executes ```!cog info``.
+
+- ``hidden`` (bool) - Determines if a cog is available for install.
+
+- ``install_msg`` (string) - The message that gets displayed when a cog is installed
+
+- ``required_cogs`` (map of cogname to repo URL) - A map of required cogs that this cog depends on.
+  Downloader will not deal with this functionality but it may be useful for other cogs.
+
+- ``requirements`` (list of strings) - list of required libraries that are
+  passed to pip on cog install. ``SHARED_LIBRARIES`` do NOT go in this
+  list.
+
+- ``short`` (string) - A short description of the cog that appears when
+  a user executes `!cog list`
+
+- ``tags`` (list of strings) - A list of strings that are related to the
+  functionality of the cog. Used to aid in searching.
+
+- ``type`` (string) - Optional, defaults to ``COG``. Must be either ``COG`` or
+  ``SHARED_LIBRARY``. If ``SHARED_LIBRARY`` then ``hidden`` will be ``True``.
+
+API Reference
+*************
 
 .. automodule:: cogs.downloader.json_mixins
 
@@ -10,14 +48,29 @@ Downloader Framework Reference
 
 .. automodule:: cogs.downloader.installable
 
+Installable
+^^^^^^^^^^^
+
 .. autoclass:: Installable
     :members:
 
 .. automodule:: cogs.downloader.repo_manager
 
+Repo
+^^^^
+
 .. autoclass:: Repo
     :members:
 
+Repo Manager
+^^^^^^^^^^^^
+
 .. autoclass:: RepoManager
     :members:
 
+Exceptions
+^^^^^^
+
+.. automodule:: cogs.downloader.errors
+    :members:
+