Fixed the warnings

[narek-h]

Summary of changes

1. validateNewState now returns the result which was set but not returned. Now the returned value is not used but can be useful later.
2. in this.setState({...}, this.validateNewState()); calls validateNewState() changed to validateNewState since it's expecting a callback.
   (there was no error on that since the method call result was 'undefined')
3. To avoid no-func-assign warnings in places

 function foo() {}
 foo = foo.bind(this);

function declarations were replaced with function expressions

var foo = function () {}

4. in a couple of places == -> === , and removed unused let props = this.props;

[narek-h]

proposal-creator: Fix warnings