Translate Joi validation errors to be a bit more helpful

[dalanmiller]

@Alanz2223 had an issue where he was accidentally adding auto_create_table to the Horizon constructor:

From Slack:

alanz2223 [12:10]  
here is my opts object 
`const options = { 
 project_name : 'test',
 auth: { token_secret: 'my_super_secret_secret' },
 auto_create_collection : true,
 auto_create_table : true
};`

But the error he was getting back wasn't so informative that auto_create_table isn't an actual option for Horizon server:

[1] "auto_create_table" is not allowed`

Now this error is pretty clear that it isn't a valid property, but maybe it could be something like:

< List of errors in Joi validation >
You have included invalid options in the Horizon constructor. 
Review the list of valid options here => https://horizon.io/docs/embed/

This could lead more people to double check?