Add detailed simulation flow installation info & helper scripts

Created by: andreaskuster

This PR aims to simplify the installation process by extending the documentation and by adding additional installation scripts (as discussed with @niwis, @bluewww, @micprog):

• add tutorial on how to use the already existing ci scripts to install the required tools for verilator software simulation
• add RISC-V proxy kernel and bootloader installation script
• removal of $ signs in commands: allows to copy and paste commands from the README.md file to the command line