Use exceptions for error handling

Use exceptions for error handling

The previous error handling strategy was very Linux kernel like, showing
influence from what I was working on while I designed this program.

Refactor the program to use exceptions, which significantly reduces the
amount of code needed for error handling. Best practices are now
followed: we only catch exceptions where we need to log a message and
rethrow, or for a complete unit of work.

Signed-off-by: Ira W. Snyder <devel@irasnyder.com>