Set KirppuVenv as interpreter for PyCharm.
Add jeditable jquery plugin for editing the DOM.
Add stubs for AJAX calls to update item price and name.
Add UI for editing, adding and deleting items.

- Does not update model yet.
- Redid the price tag structure. No more nested floats, just absolute
  positioned blocks defined in CSS. Should be more compatible and easier
  to modify.
- Moved html generation for price tags to its own template.
- Add long price tags.
Add csrf token to AJAX requests.
Require authentication for item pages.
Update model when adding items.

- Update price tag contents according to response from server.
Add deleting of items from model.

- Add barcode to the url of things related to one item.
Modify model when modifying items.
Fix item list access restriction.

- Page would not let non-staff in because it was comparing a string to int.
Add media print style sheet.
Add price tag type to model and update it when modified.
Add rest of the form elements for item add.

- Everything should work except for clear all and quantity.
Adds Clerk access codes and their management.

* Clerk access codes can be generated in bulk in admin.
* Access code can be moved from pre-generated object to bound Clerk.
* Access codes can be printed as barcodes.
* Clerk can be found directly with barcode.
Adds csrf js part

* Rename checkout output js to avoid name conflict.
Fix barcode size.

- The png version is way bigger than needed and would overflow.
Replace tab indents with spaces.
Remove duplicate crsf ajax setup.
Adds backend for simple item transactions.

* Also, Counters and their validation, Clerk login/logout.
* Basic frontend part too that currently only finds items (if clerk has
been logged in from console).
Somewhat working checkout

* Not too much of error handling yet.