Fix #512: pegsless error reading media consisting of a single element.

[blakewalters]

Addresses #512

[blakewalters]

This issue was caused by erroneously throwing an error when any input between the :start/stop media definition: delimiters or in the material data file was 1 character long. It can be traced back to the fact that the subroutine GET_INPUT_PLUS, used to read media inputs, is heavily based on (i.e. some blocks directly copied from) GET_INPUT, the routine used to read general .egsinp parameters. GET_INPUT allows for the input of a "TITLE" string for which the check on single character input is relevant (I think). But the "TITLE" input is not relevant for media inputs, so I've also stripped all references to this input parameter.