Add --verbose parameter to backstop commands to show error details

### Problem:
When running into a problem with unknown reason like the following, typically a "--verbose" parameter helps to show details:

```
$ backstop reference
COMMAND | Executing core for "reference"
clean | backstop_data/bitmaps_reference was cleaned.
createBitmaps | Selected 71 of 71 scenarios.
COMMAND | Command "reference" ended with an error after [0.574s]
COMMAND | [object Object]

```
backstop uses -v for version. Typically this is "verbose".
A verbose parameter doesn't seem to exist

### Proposed solution:
Introduce --verbose which shows more details about the process and replace -v for version with -v for verbose
Especially the [object Object] is a problem as it shows no information about the problems.

Start at the CLI option parsing used by `backstop reference`, then reproduce the shown failure and trace how its error becomes `[object Object]`. Check the existing `-v` version handling before deciding how the proposed flag change fits. Done means a verbose option exposes useful error details and the command behavior is covered by the project’s relevant checks.

Written by the indexing model from the issue text.