load.sh password prompting with basic auth

[andrewkroh]

Enhance documentation and usage info with how to use the script against an ES server with Shield + basic auth.

If you just run load.sh -url https://xyz.found.io -u admin then you will be prompted for your password for every curl request which isn't practical.

There are a few ways to pass in the password just once.

• load.sh -url https://xyz.found.io -u admin:password
• load.sh -url https://xyz.found.io -u admin:$(cat ~/pass-file) (use file to not pollute bash history with password)
• load.sh -url https://user:pass@xyz.found.io (just put user and pass in the url)

[andrewkroh]

• The scripts (both .sh and .ps1) should be updated to document how to set the password.
• Maybe add an example to the project README.
• Maybe add something to the libbeat GS guide.