Standardize Examples

- Stop ignoring -- but do ignore the generated files
- Run from root
- follow naming conventions

Preparation for #917 and #970.
this will miss the NetParameter binaryproto files which don't have an extension.  Maybe should add something like `*_iter_[0-9]+` (I have no idea what the gitignore regex syntax is like beyond `*`..)

(I've always thought the netparameter snapshots should have some kind of extension too...maybe at some point we could change both snapshot outputs to have clearer extensions like `*.NetParameter.binaryproto` and `*.SolverState.binaryproto`.)