Enhance usability

[mateus-amarante]

Description

• Introduce PROJECT_PREFIX and define PROJECT_NAME as ${PROJECT_PREFIX}_${ROS_DISTRO}
• Clean command-line options:
  • Remove options that force container recreation from command-line
  • Keep command-line options with explicit recreation meaning (-b, -f) and id-related (-p, -d)
  • Options that change container configuration can only be defined in .env file
• Move XDISPLAY to compose-add-ons
• Remove unnecessary xhost access permission to root
• Move user configuration to the entry point. It will make the deployed image more generic, allowing us to move forward on solving https://github.com/orise-robotics/ros_ws/issues/39
• Introduce the EXEC_COMMAND (-e, --exec) option to allow the user to run custom commands
• Add -r, --recreate option to force container recreation

Related Issues:

• closes #76
• closes #78
• closes #79
• closes #57

[mateus-amarante]

I'm proceeding with the merge, but feel free to add comments or open issues.