Updated Plex Notification Support

[WolfieNuke]

Workaround for https://github.com/RuudBurger/CouchPotatoServer/issues/4239
Workaround for https://github.com/RuudBurger/CouchPotatoServer/issues/3303

Added basic support for myPlex via Authentication Token. This is a
workaround until myPlex login via username/password is implemented.

Authentication Token can be obtained by:

curl -H "Content-Length: 0" -H "X-Plex-Client-Identifier: my-app" --user "myPlexUsername:myPlexPassword" -X POST https://my.plexapp.com/users/sign_in.xml

The resulting XML will have your myPlex Authentication Token

<?xml version="1.0" encoding="UTF-8"?>
  <subscription active="1" status="Active" plan="lifetime">
    <feature id="pass"/>
    <feature id="sync"/>
    <feature id="cloudsync"/>
  </subscription>
  <roles>
    <role id="plexpass"/>
  </roles>
  <entitlements all="1">
    <entitlement id="roku"/>
    <entitlement id="android"/>
    <entitlement id="xbox_one"/>
    <entitlement id="xbox_360"/>
  </entitlements>
  <username>wolfienuke</username>
  <email>wolfienuke@hotmail.com</email>
  <joined-at type="datetime">2000-00-00 00:00:00 UTC</joined-at>
  <authentication-token>XXxXXxXXxXXXXXxXxxXx</authentication-token>
</user>

I will update soon (after finals are complete) with a proper Login/Password solution for myPlex

[CouchPotatoBot]

Thanks for the pull request! Before a real human comes by, please make sure your report has all the below criteria checked

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Thanks!

[vandalon]

I've created more or less the same pull request but with less change in code.

[RuudBurger]

I think this is the same as #4380
Thanks for the PR and sorry for my late response!