added in const parsing. Each constant is read processed and added to the...

added in const parsing. Each constant is read processed and added to the kat.constants dictionary. The key is the name of the constant and the value is a namedtuple containing the value and a list of all the lines that reference the constant. Once a constant has been read it replaces the value in any string it finds, so once the command has been parsed you can not change the value of the constant and expect it to change the value of the previously parsed parameters