Add support for localized billing accounts

[vishesh92]

If your account is billed locally by AWS, e.g. by AISPL if you are in India, then the files generated for billing have AISPL in them
239874210271-aws-billing-detailed-line-items-with-resources-and-tags-AISPL-2017-01.csv.zip

This PR adds support for these types of reports.

[NitriKx]

Thanks for contributing! Billing files patterns should use "non-capturing" groups instead, and then avoid modifications on "matcher.group" calls. (http://www.rexegg.com/regex-disambiguation.html#noncap)
For instance:

Pattern.compile(".+-aws-billing-detailed-line-items-with-resources-and-tags-(?:[A-Z]+-)?(\\d\\d\\d\\d-\\d\\d).csv.zip");

[vishesh92]

@NitriKx Didn't know about that. Have updated the PR.

[NitriKx]

Thanks for the update