Add alternate names for each exercise

[danneu]

To improve searching, we could enumerate alternate names for each exercise.

For example, anyone building an exercise app would want to ensure that a user searching for "landmine row" will find "t-bar row":

{ 
    "name": "T-Bar Row with Handle",
    "alternateNames": ["Landmine Row"]
}

Now people can build their own fuzzy search: fullTextIndex(exercise.name + ' ' + exercise.alternateNames.join(' ')).

Thanks for putting this together.