Feature/reduced verbosity

The two first ones return a string containing the AST the later one
saves the AST to a file (its name is given as a string argument).

It provides getPugsVersion() and getPugsBuildInfo() functions which
return string

printLSOptions -> getLSOptions
printLSAvailable -> getLSAvailable

These new function do not print the result anymore but return a
string.

To display available or set options, one should now uses:
```
cout << getLSOptions() << "\n";
let available:string, available = getLSAvailable();
cout << available << "\n";
```

Number of grammar issues were previously output. This was useful for
early language developments but always displaying information is
irrelevant.

Note grammar issues means that the grammar itself is buggy. It is not
related to errors in user scripts.

If these environment variables are not set they are positioned to
recommended values for performance
  OMP_PROC_BIND=spread
  OMP_PLACES=treads
These variables are untouched if set by the user.

Now pugs version and build information are accessed through the '-v'
or '--version' command line options

These were useless and could eventually be problematic