updated banner's custom logo to allow logos hosted elsewhere

Super admins can now use logos hosted in in our webroot/img/layout/
folder or elsewhere (use url). I have also added some tests
to system parameters model for testing the number of system
parameters in the database.
added a new system parameter for setting the timezone

A new system parameter has been added to the system to allow the
super administrator to change the timezone. The timezone is initialized
during the installation process. If the super administrator would like
to change the timezone, they can go to system parameters under the Admin
tab and edit the system.timezone parameter. If an invalid timezone
is provided, the system defaults to UTC and a warning message will
appear warning the super administrator that an invalid time zone
is provided.
modified event model's "due_in" field to use the correct timezone

The "due_in" virtual field does not use the timezone set in the
system parameter but instead uses UTC set in webroot/index.php.
I've modifed the the model to set the timezone before generating
the field.
merged some changes from hotfix into dev
minor modifications including changing the list of valid timezones

I have removed the function that generates the list of valid
timezones because it only includes the current timezones and
not the backward compatible timezones. I have changed it to use
listIdentifiers instead.

I have fixed a bug for exporting simple evaluations to csv where
the evaluator's penalty is applied to their evaluatees' grades.

I have also fixed a bug where members that have not submitted
their evaluations but "now" is between due date and release end
date getting the final penalty instead of the expected no penalty.

Furthermore, I have removed the use of NOW() in the event model and
replaced them with date, so that the timezone set in system
parameter is used instead of the machine's timezone.
removed the "Now" button from the calendar pop-up

All date fields get a calendar pop-up. I have removed the "Now" button
from them because they are using the machine's timezone instead
of the timezone set in the system parameter. Furthermore, the functionality
is not very useful. With these reasons, I have decided to removed
the button.
modified some system tests to reflect the removal of a button

I have removed the "Now" button from the calendar pop-up previously,
so I have now updated the system tests to not use the button.

When no timezone is set in the php.ini file the a notice about an
unreliable source of the timezone will appear in test.php. This has
now been fixed by setting the timezone to UTC
fixed a bug in evaluation results for rubrics and mixeval.

For some odd reasons, sometimes a user in the system who is not in
the group will appear on the not submitted or not in group list if
they were suppose to be empty. The strangest part of this bug is
the algorithm that generates the list of user ids returns empty
(correct) but the when we put the empty array into the getUsers
function, it returns a user. I fixed the bug by checking whether
the userIds is empty. If it is, the function will just return an
empty array.

I have also fixed some controller and model tests that were missing
fixtures.
added cron job to the Boxfile

I have added a cron job to the Boxfile to send emails every
fifteen minutes, which is the lowest increment we can use.

I have also added the missing system parameter fixture to some of
the model tests.
added ids to users/courses to the sample data.

The reason for manually assigning ids to users and courses is if
the samle data is added in pagodabox the ids are incremented by 4,
which causes some problems where ids do not match in the relationship
tables.