Added AssignVersion function to Args module.
Added AssignVersion function to Versioning module.
Included Assign function as a pattern in match expression.
Included '-a' command in usage description.
Included two test cases that have been previously deleted by replacing '-a' with another, currently anonymous, letter.
Added more parameterized test cases to make the implementation even more robust for the Devil's Advocate technique.
Renamed a function.
Added more parameterized test cases to make the implementation even more robust for the Devil's Advocate technique.
Removed a redundant function.
Moved ProjectToBuild property to .config file,

because the location of solution files may vary.
Incremented minor version,

in order to indicate that the addition of an 'assign' operation is a new
feature. This resolves #16
(https://github.com/ploeh/ZeroToNine/issues/16).
extract duplicated code into UpdateVersionsInFile function
Documented the 'assign' operation.