Several fixes & improvements in the configuration menu code to handle user input.

1) FIXED: After selecting menu option 1 ("Number of VPN Client Slots available"), if the user simply pressed the <Enter> key *without* entering any new value, the currently selected value was reset to "1 2 3 4 5" regardless of the current setting.

2) FIXED: After selecting menu option 2 ("Custom PING host to determine VPN health"), if the user simply pressed the <Enter> key *without* entering any new value, the currently selected value was set to empty/NULL regardless of the current setting.

3) FIXED: When selecting menu option 2 ("Custom PING host to determine VPN health"), any user input was accepted for the IP address because there was no IPv4 address format validation.

4) FIXED: After selecting menu option 3 ("Custom Event Log size (rows)"), if the user simply pressed the <Enter> key *without* entering any new value, the currently selected value was reset to "2000" regardless of the current setting. In addition, the error message "[: 0: unknown operand" was generated.

5) FIXED: After selecting menu option 5 ("Refresh Custom Server Lists on -RESET Switch"), if the user simply pressed the <Enter> key *without* entering any new value, the currently selected value was reset to "Enabled" regardless of the current setting. In addition, the error message "[: 0: unknown operand" was generated.

6) FIXED: After selecting menu option 6 ("Provide additional WAN/Dual WAN monitoring"), if the user simply pressed the <Enter> key *without* entering any new value, the currently selected value was reset to "Enabled" regardless of the current setting. In addition, the error message "[: 0: unknown operand" was generated.

7) FIXED: After selecting menu option 7 ("Whitelist VPN Server IP Lists in Skynet"), if the user simply pressed the <Enter> key *without* entering any new value, the currently selected value was reset to "Disabled" regardless of the current setting. In addition, the error message "[: 0: unknown operand" was generated.

8) FIXED: Added user input validation for Cron Job hours & minutes

9) IMPROVED: Adjusted formatting of the number of servers to avoid left-padding with zeros while still maintaining table alignment.

10) IMPROVED: Adjusted formatting of ping values to avoid left-padding with zeros while still maintaining table alignment.

11) Various other coding improvements & fine-tuning.

Adjusted formatting of IPv4 addresses to avoid left-padding with zeros while still maintaining table alignment.

Made the display format #1 for IPv4 addresses the "new" style.

Fixes & Improvements in Configuration Menu