StringDescaper is a class that allows for adding additional \ escapes
that will be processed in a given string.

Defines are simple unary functions that apply replacements to strings.
Currently, there are two types.
* SimpleDefine - Replace all occurances of a pattern with a given
string.
* IteratedDefine - Replace occurances of a pattern with a string chosen
from a series of strings.

Most of it is documentation changes.

The rest is more work on BlockReaders, as well as a simple command
language for configuring them.