Add historysize and historyminlength config options

[digitalnyc1]

Add new config options:

• historysize: Specifies the maximum number of commands that are stored in the input box history. (Default value; 20)
• historyminlength: Defines the minimum length a command must have to be saved in the input history. (Default value: 3)

Additional notes:

• Input box history can now be disabled entirely by setting historysize to 0.
• The defaults provided were sourced from the existing hardcoded values for these variables.