[leeco] Add live.le.com functionality

[einstein95]

Please follow the guide below

• You will be asked some questions, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your pull request (like that [x])
• Use Preview tab to see how your pull request will actually look like

---

Before submitting a pull request make sure you have:

• [x] At least skimmed through adding new extractor tutorial and youtube-dl coding conventions sections
• [x] Searched the bugtracker for similar pull requests

In order to be accepted and merged into youtube-dl each piece of code must be in public domain or released under Unlicense. Check one of the following options:

• [x] I am the original author of this code and I am willing to release it under Unlicense
• [ ] I am not the original author of this code but it is in public domain or released under Unlicense (provide reliable evidence)

What is the purpose of your pull request?

• [ ] Bug fix
• [ ] Improvement
• [x] New extractor
• [ ] New feature

---

Description of your pull request and other information

This adds live.le.com functionality to the leeco.py extractor. This fixes #11788.

[einstein95]

@dstftw Fixes have been applied.

[einstein95]

@dstftw Done

[dstftw]

Squash commits.

[einstein95]

@dstftw Fixed and squashed

[yan12125]

Better to name the extractor LeLunboIE/LeLiveLunboIE/etc. "lunbo" (輪播, alternating videos) are different from ordinary live videos like http://live.le.com/music/play/index.shtml?id=3020170121012628

[einstein95]

Updated and squashed