Resolve Argument File processing differences with NUnitLite

[CharliePoole]

Fixes #126

Made the following changes to the console runner options to bring it in line with NUnitLite's features:

1. Implemented nesting of argument files to a maximum depth of 3
2. Allowed arguments in quotes to extend to multiple lines in an argument file
3. Fixed the implementation of comments in argument files
4. To keep consistency with nunitlite, I ended up eliminating the separate ArgumentsFileParser class.
5. Renamed various things for consistency.

[rprouse]

Other that the change you made to NUnitLite, this looks good. Approving so you can merge when that change is made.

[rprouse]

Looks good now, merging.