Make the start date of year configurable from the administrative dashboard

• Add "Fiscal Year Start" property (type = date, dd/mm only ) to the config object.
• Add form field to edit this value to admin/setting/date form. (change page title from "Date Formatting" to "Dates").
• Default value for new installs should be January 01. Field is required (but populated by config initialization for new installs). We also need to have a default loaded into config in session if this value isn't (yet) defined in the DB - since I don't think we can upgrade the DB config_backend field value for upgraded sites.
• Modify "Year to Date" query for contribute/dashboard to use the config value for start (and calculate year end based on fiscal start).

Note: I don't think it's necessary to store a fiscal year end - since we should always be able to calc that from the start. Any reason to do so?

— Original Post --------------
Many organizations have a fiscal year that starts on a date other than January 1. It would make the information on contributions more useful if items like the year to date totals used the fiscal year rather than the calendar year. Right now to change this you need to edit a file. It would be preferable to be able to configure this from the administration configuration screen.