Dynamically switch between navbar selections on pages

[SchrodingersGat]

Loads all page content at once, and simply switches between the available elements.

As most data are loaded via the AJAX API anyhow, this is pretty performant.

Views to refactor:

• Purchase Order
• Sales Order
• Build Order
• Company
• Part
• PartCategory
• StockItem
• StockLocation
• ManufacturerPart
• SupplierPart

Other Tasks

• Refactor "detail" view of Part page
• Fix "BOM upload" form (in Part page)
• Fix "PO Import" form (in PurchaseOrder page)
• Fix "part pricing" view (in Part page)
• Fix "import part" view (in PartCategory page)

Ref: #1683
Ref: #1673

[eeintech]

@SchrodingersGat Got excited to try it out but having some weird issue on the "Part" view (I forced reload the page):

1. Suppliers and Manufacturers tab are separated again, regression from Consolidate Manufacturers and Suppliers views #1793

2. Suppliers and Manufacturers table are missing

3. The CSS of the navbar shows a tab grey when active (aesthetic only)

[eeintech]

Also I like that the "Details" tab is gone (that means simpler interface) but didn't you want the default Part view to follow #1808 and #1673 ?

[SchrodingersGat]

Thanks for the quick review! New PR with some bug fixes