Theme engine: fix view id negotiation

The negotiation by view id does not work on web objects because it computes the view id using the trailing path relative to the nearest web object (target object).

instead the relative path of the target object should be used:

<application ...>
<view id="/module">
</view>

<view id="/module/object1">
</view>

<view id="/module/object1/sub1">
</view>

</application>