Add a membership whitelist about communitybot

[MattyIce]

Sorry for the long wait guys, I've been swamped with work the past few weeks. I've just added the whitelist option in this commit: ab06a59

I've done some testing locally but please let me know if you see any issues.

[KINGdotNET]

Hi Matt,
Looking forward to see this feature added to the community bot.
Thank you.

[rafestrape]

Hi, thanks for the published work, I'm trying to launch a communitybot
I see it very useful because if the bot lease SP delegation, the landlord is targeted as a member of the community and will be voted.
Anyway, I do not see where to enter the white list, by default anyone who makes a sufficient income is listed.
For now I can only manually delete this member, from members.json, stop and reboot communitybot.js with pm2

regards
@rafestrape

[KINGdotNET]

@rafestrape Matt still working on this feature.