Add flag to output variant name to BoM filename

[trentks]

Hi @SchrodingersGat,

Just following up from yesterdays pull you did for #37 which added support for multiple variants. I had seen the value in adding these variants names to the BoM filename, and @AngusP (author of #37) had intended himself to add support for this. I believe this patch I have written satisfies this feature.

There is a certain amount of personal preference when it comes to how this variant name actually gets included in the filename so in particular I would advise that you review line 183 of KiBOM_CLI.py (and therefore line 210 of README.md).

Cheers.

Changes made:

Changes to KiBOM_CLI.py:

• Add logic to include variant name in filename if flag is set.
• Clean up some rogue whitespace.

Changes to README.md:

• Add description for new includeVariantName flag.
• Add include_variant_name flag to default bom.ini.
• Fix inconsistencies in capitalisation of "BoM".
• Add missing include_version_number flag to default bom.ini.

Changes to bomlib/preferences.py:

• Add support for include_variant_name, includeVariantName where appropriate

[SchrodingersGat]

This all seems quite reasonable. Thanks for the contribution!