User activity tracking: schema and IDL

User activity tracking: schema and IDL

* Adds 2 new tables and IDL classes.  The first is a configuration table
  used for defining activity types (config.usr_activity_type).  The
  second is for tracking activity events.  A user activity event is
  defined as a combination of user, action (e.g. login), the interface
  or 3rd-party responsible for the action (e.g. opac, staffclient,
  libraryelf), and the OpenSRF ingress (i.e. the mechanism through which
  the action was delivered: e.g. gateway, translator, xmlrpc).

* Includes a front-facing stored procedure (actor.insert_usr_activity),
  used for creating new activity entries.

* Adds seed data for some default activity types and reserves the first
  1000 IDs for system use.

Current default values for "ewho":

opac
staffclient
selfcheck
authproxy
ums
libraryelf
ezproxy

Current default values for "ehow" (ingress, some inherited from
opensrf):

opensrf (default)
gateway-v1
translator-v1
srfsh
--
sip2
xmlrpc
remoteauth
apache (default mod_perl/apache mod entry point)

Signed-off-by: Bill Erickson <berick@esilibrary.com>