Admin - Added capability for site-level invoice prefixes

Admin users can create custom invoice prefixes for different contracts.

Go to System > Admin [3] > Types > Contracts [1] > Add [2]/Edit Contracts popup

The Description [1] data entry field and the Invoice prefix [2] data entry field can be alphanumeric with a 25 character/number limit.

The Invoice number length [3] is limited from 1 to 12, for example:

Invoice number length set to 3.

Invoice start number [4] range is limited from 1 to 999.

To generate an invoice, please use Quick Ref Create an invoice.