Changed C-style names to Go-style names in Go code.
Implemented Lbfgsb solver construction and setup.

* Added constructor (but zero value is still valid solver object).
* Added methods for setting bounds and parameters.  Can chain for fluent
  interface.
* Added dimensionality field to ensure solver gets initialized and that
  the dimensionality remains constant across invocations.
* Renamed 'debug' to 'debugLevel'.
Reworked example program.

* Builds (for now) by using local package.
* Added ignoring of example program executable.
* Reordered example to start more simply and increase in complexity.
* Switched roles of sphere and Rosenbrock functions in support of
  increasing complexity.
* Updated to use Lbfgsb solver setup.
Changed all Lbfgsb methods to pointer receivers.  Oops.
Fixed things to get example program running.

* Ensured return after error.
* Ensured bounds arrays are allocated.
* Changed bounds control array to C type because used only in C.
* Added terminator to ExitStatus.String().