Re-define custorder item status/event codes enum

pretty sure this is good enough to go live with...?

Add `special_order` flag for CustomerOrderItem

also add `flagged` flag

and copy all product key fields when making order from batch

Must pass rows to `make_new_order()` for custorder batch

also allow passing `new_order_id` if `batch.id` is not wanted for order

Improve UOM choices for product info

better represent items sold by weight, for new/edit custorder

Update usage of `get_product_key_field()`

avoid deprecation warnings

Add `get_person()`, `get_customer()` etc. to AppHandler

make it delegate to appropriate handler for each method. also the
various handler methods with actual logic, are a bit more generic in
what they accept

Massive overhaul of "generate project" feature

previous incarnation was woefully lacking. new feature is much more
extensible. still need to remove old POS integration specifics in
some places.

and a couple of unrelated things that snuck in..

- deprecate `rattail.util.OrderedDict`
- deprecate `rattail.util.import_module_path()`
- deprecate `rattail.util.import_reload()`

Let cases and/or units be (dis)allowed for new custorder

at least this sets the stage, probably more tweaks needed to fully
support the idea

Add common normalize logic to ProductsHandler

about dang time..now still need to enhance and use it everywhere

Misc. flexibility improvements for vendor catalog batch

- ExcelReader now should ignore "pseudo-empty" columns
- add `ProductsHandler.get_case_size()` method
- vendor catalog batch input need not contain case sizes (we copy them
from product master if not)
- vendor catalog batch input need not contain vendor item codes either
- vendor catalog product lookup now tries global default logic
first (then falls back to its own traditional logic)
- generic catalog parser lets handlers do more of the work

Add support for finding past items, for new custorder

also misc. tweaks for new custorder feature

Add `get_past_products()` method for custorder batch handler

also add more to `get_product_info()`

Add some product info fetchers to custorder batch handler

for easier customization

Add `add_product()` method for custorder batch handler

let it be repsonsible for adding a new item to the order

Restore "pending" customer when unassigning batch contact

unassign means "unset contact uuid" essentially, i.e. unassign the
"proper" contact. but if "pending" contact info is there, restore it

Limit autocomplete results for customer/phone lookup in new custorder

otherwise it's possible for the whole thing to bog down and freeze the
browser page...

Add `why_not_add_product()` for custorder batch handler

let it declare any reason it likes for preventing the item add

Add `update_pending_customer()` for custorder batch handler

and perhaps more importantly, `validate_pending_customer_data()`

this was needed for sake of unique email address checks

Add `contact_name` for custorder and batch

so that we have something handy to easily sort/filter by etc.

Save pending customer reference when creating new custorder

i.e. when executing new custorder batch

Add "contact update request" workflow for new custorders

if user requests contact info be updated on the customer record, then
"someone" (staff) should receive an email with that info

Add `get_contact_emails()` and `should_restrict_contact_info()`

for custorder batch

Add `get_contact_phones()` method for custorder batch handler

for presenting options to user when making new order

Add `get_contact_notes()` method for custorder batch handler

not sure if this is quite the right approach, but better than we had
before at least. may need to get certain "notes" independently,
e.g. "customer has invalid phone/email" type flags

Add "all" enum values for custorder item status, event

also attach "initiated" event(s) when creating new custorder

Make custorder batch handler responsible for (un)assigning contact

it also will update the contact info, i.e. phone/email

Add "custom" customer autocomplete for new custorder handler

can search by name or phone number

Some tweaks for customer orders

- improve how case size is determined
- auto-delete items when order is deleted