There was an API change in python-axolotl

This fixes some deprecation warnings related to Gtk.Color and restructures
code and formatting according to pylint suggestions

If Open Link in Browser is selected as default action for left clicking an image,
the user would get a warning when clicking an encrypted image. Fall back to open
image directly instead of issuing a warning dialog.

Fixes #412

This reverts commit e53150c9

The way BLOBs are written to the database has changed in python3
So we read all BLOB values cast them to BLOB then write them back to
the table

Fixes #402, #278