WL#1825: Dynamic length numeric fields

This is feature request from one of the customers, which I remember popping 
up a few times. 

One stores numbers in the column, but in most cases it is "NULL", the numbers
are also mostly in the low range so tinyint would cover 90% of cases and smallint 
99%.  There are however some large numbers which can be stored so one has to use 
BIGINT column type. 

We could add similar to VARCHAR() numeric field to target it, which could 
consume from  1 byte for NULL value to 9 bytes for BIGINT.

The economy might look small but there are some applications which have hundreds
of columns in table to represent arrays.