[docs] mfg and accounts module completed

docs/user/accounts/docs.user.accounts.opening_entry.md

@@ -0,0 +1,10 @@
+---
+{
+	"_label": "Opening Entry"
+}
+---
+
+If you are a new company you can start using ERPNext accounting module by going to chart of accounts.
+
+However, if you are migrating from a legacy accounting system like Tally or a Fox Pro based software, please visit [Opening Entry](docs.user.setup.opening.html)
+

docs/user/accounts/docs.user.accounts.purchase_invoice.md

@@ -44,7 +44,7 @@ To see entries in your Purchase Invoice after you “Submit”, click on “View
 
 ---
 
-#### Is a purchase an “Expense” or “Asset”?
+#### Is purchase an “Expense” or an “Asset”?
 
 If the Item is consumed immediately on purchase, or if it is a service, then the purchase becomes an “Expense”. For example, a telephone bill or travel bill is an “Expense” - it is already consumed.