CLC-2088 Allow logging to stdout via ENV or settings file

https://jira.media.berkeley.edu/jira/browse/CLC-2088

EXAMPLE 1:
```
calcentral> rails c
...
>> cp.request_uncached('nosuchpath')
nil

>> CalcentralLogging.init_stdout

>> cp.request_uncached('nosuchpath')
[2013-06-23 06:33:42] [INFO] CanvasProxy - Making request with @fake = false, options = {:method=>:get, :uri=>"https://ucberkeley.test.instructure.com/api/v1/nosuchpath"}, cache expiration 2100
[2013-06-23 06:33:43] [WARN] CanvasProxy connection failed for URL 'https://ucberkeley.test.instructure.com/api/v1/nosuchpath', UID 211159: 404 {"status":"not_found","error_report_id":59350455,"message":"An error occurred."}
nil
```

EXAMPLE 2:
```
calcentral> rake canvas:make_csv_files
[RailsAdmin] RailsAdmin initialization disabled by default. Pass SKIP_RAILS_ADMIN_INITIALIZER=false if you need it.
config.cache_store is now #<ActiveSupport::Cache::DalliStore:0x47f959 @data=#<Dalli::Client:0x143692f @servers=["localhost"], @options={:expires_in=>172800, :namespace=>"3ff3557d9d6906e19adf2218579fc4fe887a6595", :race_condition_ttl=>10, :compress=>nil}, @ring=nil>, @raise_errors=false, @options={:expires_in=>172800, :namespace=>"3ff3557d9d6906e19adf2218579fc4fe887a6595", :race_condition_ttl=>10, :compress=>nil}>
Shutdown completed cleanly

calcentral> rake canvas:make_csv_files LOGGER_STDOUT=true
...
[2013-06-23 07:18:12] [WARN] Canvas section has SIS ID but course does not: 1237013,SEC:2013-C-7372,1093165,,2013-C-7372,active,,,90242,
[2013-06-23 07:18:13] [INFO] Will refresh 5 Canvas enrollment records for TERM:2013-C
[2013-06-23 07:18:13] [INFO] Will refresh 3 Canvas user records
[2013-06-23 07:18:13] [INFO] Generated CSV files = {:users=>"tmp/canvas/canvas-2013-06-23-users.csv", :enrollments=>{"TERM:2013-C"=>"tmp/canvas/canvas-2013-06-23-TERM_2013-C-enrollments.csv"}}
Shutdown completed cleanly
```