Change Variable Names in ParserOfT

Changed variable names in methods accepting TextReader.
Organizing Parse Even More

Moved parsers into new folder "Parsers." Separated character parsers and
numeric parsers into sub-classes Characters and Numerics. Also added
sub-class "Parsers" for identifier.
Updated code to accept new sub-classes. Haven't checked tests yet...
Added new "Then" combinator to allow for just a class to be passed in
when the lambda for Then would be a => second.Return(a).
Added new Contained combinator to allow for only one parser to be used
for both the open and close containers. Updated Token combinator to use
this.