Sets key in this to value.
A convenience variant of @set for string arrays. If value is
null, then key is set to be the empty array.
It is a programmer error to give a key that isn't specified as having an array of strings type in the schema for
this.
| this |
a Settings object |
| key |
the name of the key to set |
| value |
the value to set it to, or null |
|
true if setting the key succeeded, false if the key was not writable |