Updated sub regions (AS923_1C+, AU915_SB1, EU868_B+)

[MuratUrsavas]

Issue (https://nebraltd.atlassian.net/browse/NEBD-71) (Closes #118)

New sub region plans has been added. Some of the existing ones has been updated with notes.

Checklist

• [ ] Tests added
• [ ] Cleaned up commit history (rebase!)
• [ ] Documentation added
• [ ] Thought about variable and method names

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[MuratUrsavas]

@pritamghanghas Yep! Actually EU868_x variants are all the same but they have probably prepared for some future changes.

[shawaj]

@MuratUrsavas we need to remove all the comments from the JSON files or it will break things.

We ran into this issue before... ref https://github.com/NebraLtd/hm-pktfwd/pull/106

[shawaj]

Also @MuratUrsavas you need to add them to here https://github.com/NebraLtd/hm-pktfwd/blob/master/pktfwd/config/region_config_filenames.py

[MuratUrsavas]

@shawaj Thanks for pointing them out.

[MuratUrsavas]

Done with #139