Enhance jQuery selector to handle zk widget's ID

Ready since 2010/03/18.

For example,

1. jq('div > $abc') will return the two div(id=abc) elements.
2. jq('div$win1 > $abc') will return the div element inside the win1 window.
3. jq('$abc') will only return the first match element for better performance.
4. jq('div$abc') will return the two div(id=abc) elements.

<zk>
<window id="win1">
<div id="abc" class="abc"/>
</window>
<window id="win2">
<div id="abc" class="abc"/>
</window>
</zk>

Update the specification, the $ sign is used for ZK widget's ID and the @ sign is used for ZK widget's tag name.

For example,

1. jq('@window > $abc') will return the two div(id=abc) elements.
2. jq('@window[class~="abc"] @div') will only return the div where is inside the window with "abc" CSS class name.
3. jq('div$win1 > $abc') will return the div element inside the win1 window.
4. jq('$abc') will return all the elements that match from the given id.
5. jq('@div') will return all the elements that match from the given tag name.
6. jq('@window:first') will return id="win1"
7. jq('@window[border="normal]"') will return id="win1".

<zk>
<window id="win1" class="abc" border="normal">
<div id="abc" class="abc"/>
</window>
<window id="win2">
<div id="abc" class="abc"/>
</window>
</zk>