Adding a project for the Las Vegas Metro area

[eric-hendrickson]

👋 I did some awesome work for the Pelias project and would love for everyone to have a look at it and provide feedback.

---

Here's the reason for this change 🚀

I needed a Pelias instance for the Las Vegas Metro/Clark County, Nevada area, so I added this.

---

Here's what actually got changed 👏

Copied projects/portland-metro and adapted it to Las Vegas Metro. This of course involved changes to pelias.json. I deleted the blacklist directory and made the files under synonyms a little more vanilla (I may change add it more but to be honest I don't fully understand how the synonyms help, since test cases 37-40 in search_address.json are designed to fail). I also added some test cases, although not as many as with portland-metro.

EDIT: I realize that some resources are more locally specific while others are more Nevada specific. Please let me know if you think it would be a better idea to make this a project for Nevada as a whole. I also took the liberty to fix the spelling in other projects' custom_street.txt files ("fourth" was previously spelled as "forth")

---

Here's how others can test the changes 👀

Run pelias test run. Feedback on the quality of my tests may not be necessary, but they would be appreciated.

[missinglink]

Hi, I took the liberty to clean up your commits, hope thats ok 🙏
Thanks for your contribution!