Better and smarter top-level bash script

[rhl-bthr]

• Support using both long options and short options. The sequence of options should be pretty flexible.
• It should automatically detect the P4 language version (P4_14 vs P4_16). See Barefoot Academy's p4_build.sh script for ideas on this.
• Interactive Mode: The top-level script should run the interactive mode by default and ask all missing options showing their default values. If certain options are specified by the user, it should not ask again for them, but only ask for remaining options. If the top-level script invocation specifies all options (especially the targets), then interactive mode should not be triggered.