Allow storing numeric data types

[kzarzycki]

I would like to store numeric fields in TrailDB, e.g. "price of the item bought by user" and be able to range filter events based on that, like "find user purchases of items which cost > 100$" .

Of course currently TrailDB allows you to store numeric data, but it considers it a string. That makes storage inefficient (with dictionary encoding). Additionally, filtering the data based on range requires first decoding the values from stored items.