Reference docs (#308)

* Add information on build order reference

* Add reference field description for purchase order

* Add reference information for SalesOrder

* Updated images for build orders

* Update settings information

* Add note regarding python string formatting

* Add some more screenshots

* Improved BOM documentation

* Improve BOM documentation further

* Split  "BOM Export" onto separate page

* Rearrange docs pages

* Add image to fill TODO entry

* Split out part scheduling page

docs/build/bom_import.md

@@ -0,0 +1,49 @@
+---
+title: BOM Import
+---
+
+## Importing BOM Data
+
+Uploading a BOM to InvenTree is a three steps process:
+
+1. Upload BOM file
+0. Select matching InvenTree fields
+0. Select matching InvenTree parts.
+
+To upload a BOM file, navigate to the part/assembly detail page then click on the "BOM" tab. On top of the tab view, click on the <span class='fas fa-edit'></span> icon then, after the page reloads, click on the <span class='fas fa-file-upload'></span> icon.
+
+The following view will load:
+{% with id="bom_upload_file", url="build/bom_upload_file.png", description="BOM Upload View" %}
+{% include 'img.html' %}
+{% endwith %}
+
+#### Upload BOM File
+
+Click on the "Choose File" button, select your BOM file when prompted then click on the "Upload File" button.
+
+!!! info "BOM Formats"
+	The following BOM file formats are supported: CSV, TSV, XLS, XLSX, JSON and YAML
+
+#### Select Fields
+
+Once the BOM file is uploaded, the following view will load:
+{% with id="bom_select_fields", url="build/bom_select_fields.png", description="Select Fields View" %}
+{% include 'img.html' %}
+{% endwith %}
+
+InvenTree will attempt to automatically match the BOM file columns with InvenTree part fields. `Part_Name` is a **required** field for the upload process and moving on to the next step. Specifying the `Part_IPN` field matching is very powerful as it allows to create direct pointers to InvenTree parts.
+
+Once you have selected the corresponding InvenTree fields, click on the "Submit Selections" button to move on to the next step.
+
+#### Select Parts
+
+Once the BOM file columns and InvenTree fields are correctly matched, the following view will load:
+{% with id="bom_select_parts", url="build/bom_select_parts.png", description="Select Parts View" %}
+{% include 'img.html' %}
+{% endwith %}
+
+InvenTree automatically tries to match parts from the BOM file with parts in its database. For parts that are found in InvenTree's database, the `Select Part` field selection will automatically point to the matching database part.
+
+In this view, you can also edit the parts `Reference` and `Quantity` fields.
+
+Once you have selected the corresponding InvenTree parts, click on the "Submit BOM" button to complete the BOM upload process.