Updates after 2nd tutorial

Created by: jmduarte

Updates after a successful 2nd tutorial:

• simplified conda installation with just a single environment.yml (that installs master of hls4ml and qkeras`)
• added a script to setup a jupyter kernel with Vivado
• cleaned up some unnecessary code in plotting.py
• simplified/removed some of the unnecessarily repeated model.predict() commands
• added a second legend to the plots

@thesps let me know what you think