Support for automatic Kdesk icon hooks (startup and refresh)

 * provide for automatic icon hooks upon kdesk startup and refresh signals
 * reorganized hook code
 * support for case insensitive icon names to invoke hooks
 * improved search algorithm to find icons during hook invocation
 * improved effiency: icon is only redrawn if hook changes at least 1 attribute
Merge pull request #46 from KanoComputing/automatic-hooks

Support for automatic Kdesk icon hooks (startup and refresh)