As a user, I want to be able to reset the Timezone setting to its default value

Problem Definition

Once an explicit value has been set for the Timezone setting in the User Profile area, it is not possible to reset it to its default value.

How to reproduce this behaviour:

1. open the user settings, and set an explicit value for the timezone
2. the cru_timezone column in the cru_user_profile table will be updated with the value set in the user interface
3. open the user settings again, and set the default timezone (this is the first one in the list)
4. the cru_timezone column will not be updated with an emtpy/null value, therefore the previously set timezone is still set
5. when reopening the user interface, the previously set timezone is selected in the drop down

Note: for FishEye/Crucible < 4.x, the cru_timezone column can be found in the cru_user table

Suggested Solution

Provide the ability to reset the Timezone setting to the default value.