docs: New app bar training docs

android.app.ActionBar} (introduced in API Level 11). Valid values:

          <table>

            <tr><th>Value</th><th>Description</th></tr>

            <tr><td><code>ifRoom</code></td><td>Only place this item in the Action Bar if

there is room for it.</td></tr>

            <tr><td><code>ifRoom</code></td><td>Only place this item in the

            Action Bar if there is room for it. If there is not room for all

            the items marked <code>"ifRoom"</code>, the items with the lowest

            <code>orderInCategory</code> values are displayed as actions, and

            the remaining items are displayed in the overflow menu.</td></tr>

            <tr><td><code>withText</code></td><td>Also include the title text (defined

by {@code android:title}) with the action item. You can include this value along with one

of the others as a flag set, by separating them with a pipe {@code |}.</td></tr>

            <tr><td><code>never</code></td><td>Never place this item in the Action Bar.</td></tr>

            <tr><td><code>never</code></td><td>Never place this item in the Action Bar. Instead, list the item in the Action Bar's overflow

            menu.</td></tr>

            <tr><td><code>always</code></td><td>Always place this item in the Action Bar.

Avoid using this unless it's critical that the item always appear in the action

bar. Setting multiple items to always appear as action items can result in them overlapping