TNT xread correct the handling of "- interpretation flag"

[recursion-ninja]

There is a flag in TNT XREAD commands to determine how to interpret the - char when encountered in a character.

The - char can be interpreted in one of two ways:

1. All non-gap states observed
2. Only the gap state observed

We must look for the flag in the TNT file and correctly interpret the - symbol in the TNT parser's post-processing pass.