[docs] made structure for user docs combining manual and existing help

docs/docs.user.buying.supplier_quotation.md

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+---
+{
+	"_label": "Supplier Quotation"
+}
+---
+If you have multiple **Suppliers** who supply you with the same **Item**, you usually send out a message (Request for Quote) to various **Suppliers**. In many cases, again specially if you have centralized buying, you may want to record all the quotes so that 
+
+- You can easily compare prices in the future 
+- Audit whether all Suppliers were given the opportunity to quote.
+
+Supplier Quotations are not necessary for most small businesses. Always evaluate the cost of collecting information to the value it provides! You could only do this for high value items.
+
+You can make a Supplier Quotation directly from:
+
+> Buying > Supplier Quotation > New Supplier Quotation
+
+or directly from the Purchase Request.