`$ANY$ ` expressions do not validate correctly

[bennmapes]

Currently when using an $ANY$ expression in a visibleIf statement it does not validate correctly on number fields or anything without a length property such as numbers, booleans etc.

The way it's currently testing for validity of a value with $ANY$ is with this:

ngx-schema-form/projects/schema-form/src/lib/model/formproperty.ts

Line 253 in 426af24

valid = value && value.length > 0;

I'm proposing we change that to something that can handle all possible values such as:

if(Array.isArray(value)) {
  valid = value.length > 0;
} else if(typeof value === "number") {
  valid = true;
} else if(typeof value === "boolean") {
  valid = true;
} else if(typeof value === "string") {
  valid = value !== '';
} else if(typeof value === "object") {
  valid = value !== null && value !== {};
}

Pull request with this change to follow. Feel free to share thoughts/improvements on this solution.