Support edit order of the fields in table

[Chang Wei 昌維]

Hi Postgres community: I think support editing order of the fields in 
table is a useful feature. I have known that the order of fields will 
effect the data structure of rows data, but I think we could add a extra 
information to identify the display order of fields but not effect the 
rows data, and the order identification is only used to display in order 
while execute `SELECT * FROM [table_name]` and display the table 
structure on GUI tools like pgAdmin.

Now, we must create a new view and define the order of fields if we need 
to display the fields of  table in a order of our demand, it is not a 
good way.


Many Thanks

Chang Wei