Create a new discount system integrated with the parts framework
   calpoly/api/discounts.py: Create API routes for the new Discount table
   calpoly/api/receipts.py: Modify receipt create POST route to handle discounts as part of ReceiptItem objects, and add new '/finalize/' route that does additional preparation of the receipt
   calpoly/finance/models.py: Add a Discount table, and add columns to the ReceiptItem object to support the discounts
   calpoly/frontend/static/templates/consoles/parts.html
   calpoly/frontend/static/css/consoles/parts.css: Move the part table inside a div and add a box for selecting one of multiple discounts
   calpoly/frontend/static/js/Part.js: Simplify renderToLineItem method. Possible performance expense.
   calpoly/frontend/static/js/consoles/parts.js: Rewrite console to handle less receipt creation duties; pass those off to the server via the receipt finalize route
   calpoly/frontend/static/js/fake.js: Modify fake receipt generation to comply with new JSON
   calpoly/frontend/static/js/ieee.js: Add ability to handle negative money amount to toMoney method
   calpoly/frontend/static/loading_blue.gif: new loading icon for continue button in parts console
   calpoly/frontend/templates/receipts/single_receipt.html: Better part descriptions in the table
   calpoly/parts/models.py: Made spacing in Kit object match other spacing
   calpoly/parts/utils.py: Fixed how Name/Value pairs without a value are handled in engineering_notation function
   migrations/versions/1fd0ec64a0a4_add_discount_table.py: Add discount table and new columns to ReceiptItem
   setup.sql: Added two discounts, "IEEE Member", and "Refund"
Fix displaying is negative dollar values in receipts
   calpoly/frontend/static/js/consoles/finance.js: Add more width to parts listings
   calpoly/frontend/templates/receipts/single_receipt.html: Put the negative sign before the dollar sign instead of after
Added ability to handle manual receipt entries on the server side
   calpoly/api/receipts.py: Added loop to handle manual entries
Remove restriction preventing refunds
   calpoly/api/receipts.py: Remove <= 0 requirement from receipts route
PEP8
   calpoly/api/discounts.py,
   calpoly/api/receipts.py,
   calpoly/finance/models.py: Style
Merge pull request #329 from CalPolyIEEE/better-discounts

Better discounts