Added a V command to the file directory list to allow viewing a file. This is...

Added a V command to the file directory list to allow viewing a file.  This is done by reading ctrl/file.cnf (based on the read_file_config function in src/sbbs3/scfglib2.c), matching the filename extension in the list, and if found, it runs the file view command using bbs.exec().

If possible, it would be useful to add the ability for sysops to move and delete files from this file lister (as in the stock file lister), but I'm not sure how feasable that would be right now.