fixed bug when attribute is actually an "0"

When we set an attribute in XML file like this: "some_value"="0"
(The value with this attribute accept any integer include "0")
Then, we use XmlHelper to get the value with: "$value = XMLHelper::get($element, 'some_value', 3);"
The value will be "3" not "0"

These changes could fix this kind of problem
Merge pull request #86 from gourrymk2/fix-bug-xml-helper

[FixBug] Fixed bug when attribute is actually an "0"
Update UriHelper.php
Searchtools can hide label for filters. Fixed #85
JRegistry compat
Enhance ListModel. Fixed #87
Save & Close can checkin item. Fixed #88
Elfinder should check language file exists or not. Fixed #89
Elfinder Should use config. Fix #90
Elfinder ConnectView should use $input->getPath to get root. Fixed #91
GridView setTitle should use $icon instead hard coded. Fixed #92
Highlight query
MISC update
Move elfinder
Now Elfinder can use dynamic dirs
Remove no need ns
Prep 2.0.6 dev
Update ConnectView.php
Add symfony/yaml
Update NullObject.php