Deprecate the PatternUI annotation

[ujhelyiz]

As the goal of the PatternUI annotation and the QueryExplorer are very similar, I propose to deprecate the PatternUI, and its single parameter should be made available in QueryExplorer.

The following steps are needed:

• Add an attribute to the QueryExplorer annotation to hold the label previously defined in the PatternUI annotation.
• Modify the Query Explorer/Databinding code to use this new parameter.
• Set the deprecated property of the PatternUI annotation true in the plugin.xml.
• Add a comment to the PatternUI annotation that the QueryExplorer should be used instead.

Moved from issue #276.

[ujhelyiz]

Is it necessary for the QueryExplorer#message attribute to be mandatory? This causes errors in various cases.