Make max temp table size settable

The fixed max temp table size would be not enough for complex queries. For example, a query with aggregate function and GROUP BY statement on 10 GB data on my two voltdb nodes. Making it settable should be better and flexible.

Not sure why my exmaples does not show. Copy it again:
"
    <systemsettings>
        <temptables maxsize="500"/>
    </systemsettings>
"