Set up branch node to add self as listener.

Takes in the name (or pid, but this is not really useful if the input
stream process is terminated/restarted) of a {file,socket}_input
process. Adds itself as a listener of that process during init/1.
Updated ydb_input_stream module.

Now takes an additional parameter of the name that is used when
registering the {file,socket}_input process, which the branch node is
able to use to add itself as a listener.

Need to add documentation and contracts for functions.
Created ydb_input_stream_sup module.

Implements supervisor behaviour (for input streams). Support
registering an input stream via register/2. Uses the name given to the
{file,socket}_input process to recognize the input stream internally.
Stubbed out ydb_query module.

Currently takes an ambiguous query specification as a paramter. Hard to
write this module until the planner exists.
Created ydb_query_sup module.

Implements supervisor behaviour (for queries). Supports registering a
query via register/2. Currently requires a name be given to the query
to recognize it internally.
Added support for registering name to supervisors.

Used by top-level supervisor to refer to the input stream supervisor
and the query supervisor processes.
Updated ydb_sup module.

Supervises two processes: (1) a process for supervising all input
streams, and (2) a process for supervising all queries. Registers the
names of these processes, so the user has an easier way to interface
with the system by only needing to keep track of the main supervisor
process.
Fixed issue where type was specified as worker instead of supervisor.
Created system-level in ydb_app.
Merge branch 'local'