Better handling of binary data

There are a couple of issues with how pgmanage displays bytea columns:
1. In Query Tab bytea is displayed as base64 encoded string, even though ```show bytea_output``` outputs "HEX"
2. Discrepancy between Query and Data Editor: Cells in Data Editor don't show anything, the API response for data edtior grid has incorrect values like "<memory at 0x7f9911f90940>"