title: lookback API where filter with multiple conditions
body: <p>When using loopback API, is 'AND' operator redundant in 'where' filter with multiple conditions?
  For example, I tested the following two queries and they return the same result:</p>
  
  <pre><code>&lt;model&gt;.find({ where: { &lt;condition1&gt;, &lt;condition2&gt; } });
  &lt;model&gt;.find({ where: { and: [&lt;condition1&gt;, &lt;condtion2&gt;] } });
  </code></pre>
  
  <p>To be more specific, suppose this is the table content:</p>
  
  <pre><code>name   value
  ----   -----
  a      1
  b      2
  </code></pre>
  
  <p>When I execute 'find()' using two different 'where' filters, I get the first record in both cases:</p>
  
  <pre><code>{ where: { name: 'a', value: 1 } }
  { where: { and: [ { name: 'a'}, { value: 1 } ] } }
  </code></pre>
  
  <p>I've read through the API documents, but didn't find what logical operator is used when there are multiple conditions. 
  If 'AND' is redundant as shown in my test, I prefer not using it. But I just want to make sure if this is true in general, or if it just happens to work with postgreSQL which I'm using.</p>