Logical operator consistency

[PRR24]

Currently logical operators (like and, or) in the helpers are based on Javascript if operator.
Please consider implementing logical operators bases of the way of Handlebars if operator functions.
So that
{{#if (and a b)}} smth {{/if}} would act 100% as {{#if a}}{{#if b}} smth {{/if}}{{/if}}
Currently there are cases (for example empty array) where these two constructions differ and it may result unexpected behaviour in constructions like:

{{# if (or a b)}}
  Found:
  {{#if a}}Element a{{/if}}
  {{#if b}}Element b{{/if}}
{{/if}}

Thank you.