Make the return value of integer variables types ordinary integers unless absolutely necessary
Support auto-update of row counter variable for tables

A SNMP variable of an integer type can be created and passed in to the Table() constructor in the "counterobj" property. netsnmpagent will then auto-increase this variable's value whenever a new row is added with addRow(). Naturally the variable should be exposed read-only.
Add a function to clear the table (ie. remove all table rows)