Refactor CLI and filereader to allow PeTTa to work as a transpiler

[rmgaray]

PeTTa currently cannot be used as a transpiler because it does not output the generated Prolog clauses when translating MeTTa code. It also always executes all goals, which is not what we want when running it as a compiler. This PR fixes that:

• Modified load_metta_file and other clauses to return the generated Prolog program in addition or instead of the execution results.
• Added new runtime option to disable MeTTa code execution and refactored process_form to use it.
• Modified the filereader module to take into account the already existing runtime option silent and disable the debug messages when interpreting/compiling.
• Removed ad-hoc option parsing in fileloader.pl and introduced a more principled CLI using the optparse library. PeTTa has now two modes of operation: compiler and interpreter.
• Generated 'add-atom' clauses for all MeTTa sexprs when compiling MeTTa programs.
• Add runtime clauses to generated output
• Modified translate_expr to print the results of each runnable. This is achieved by optionally adding a write clause at the end of each runnable body. This is only done for top-level MeTTa forms and whenever we are in compiler mode, not when interpreting MeTTa programs the usual way.
• Make compiled clauses dynamic (we need this to fully support MeTTa).
• Run all tests in compiled mode?