Allow using bashly-settings.yml instead of settings.yml

[DannyBen]

Closes #381

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Before this PR:
Settings file location is either settings.yml or whatever is defined in BASHLY_SETTINGS_PATH environment variable.

After this PR:
Settings file location is either bashly-settings.yml, or settings.yml or whatever is defined in BASHLY_SETTINGS_PATH environment variable.

https://github.com/DannyBen/bashly/blob/16ba317aeca415736ee5687fae130dbfb520acc1/lib/bashly/settings.rb#L103-L111

In addition, the Settings specs were refactored a bit to ensure the specs work with a known state of the Settings eigenclass.

[DannyBen]

@EmilySeville7cfg - this is done only to satisfy the JSON schema use case you mentioned.

Is this an acceptable compromise?

[EmilyGraceSeville7cf]

Is this an acceptable compromise?

Sure, it is the best decision I see here.