Skip packing by default if no changed files are found

[tinygiant98]

Added behavior to skip packing the erf if:

• the target file already exists
• no changed files are found for the target
• the user didn't pass the --packUnchanged option

If skipped, will display a skipped message. If the file exists, and there are no changed files, and the user passes the --packUnchanged option, an info message will display stating no new files were found before continuing the pack process.