added export and improved import

public/files/import/bills.csv

@@ -1,2 +0,0 @@
-"bill_number","order_number","bill_status_code","billed_at","due_at","amount","currency_code","currency_rate","vendor_id","vendor_name","vendor_email","vendor_tax_number","vendor_phone","vendor_address","notes","category_id"
-"987654","","received","2017-11-30","2017-12-07","10.0000","USD","1.00000000","1","Test Vendor","test@vendor.com","","","","","4"

public/files/import/customers.csv

@@ -1,2 +0,0 @@
-"user_id","name","email","tax_number","phone","address","website","currency_code","enabled"
-"","Test Customer","test@customer.com","","","","","USD","1"

public/files/import/invoices.csv

@@ -1,2 +0,0 @@
-"invoice_number","order_number","invoice_status_code","invoiced_at","due_at","amount","currency_code","currency_rate","customer_id","customer_name","customer_email","customer_tax_number","customer_phone","customer_address","notes","category_id"
-"INV-00001","","sent","2017-11-30","2017-12-07","10.0000","USD","1.00000000","1","Test Customer","test@customer.com","","","","","3"

public/files/import/items.csv

@@ -1,2 +0,0 @@
-"name","sku","description","sale_price","purchase_price","quantity","category_id","tax_id","enabled"
-"Test Item","test-item","","10.0000","5.0000","1","5","2","1"

public/files/import/payments.csv

@@ -1,2 +0,0 @@
-"account_id","paid_at","amount","currency_code","currency_rate","vendor_id","description","category_id","payment_method","reference"
-"1","2017-11-30","10.0000","USD","1.00000000","1","","4","offlinepayment.cash.1",""

public/files/import/revenues.csv

@@ -1,2 +0,0 @@
-"account_id","paid_at","amount","currency_code","currency_rate","customer_id","description","category_id","payment_method","reference"
-"1","2017-11-30","10.0000","USD","1.00000000","","","3","offlinepayment.cash.1",""

public/files/import/vendors.csv

@@ -1,2 +0,0 @@
-"name","email","tax_number","phone","address","website","currency_code","enabled"
-"Test Vendor","test@vendor.com","","","","","USD","1"