CategoryBuilder is added. Category functions moved there
CategoryBuilder is cleaned from "nodeType" parameters
Adapting SearchModel for new implementation
Merge branch 'Sitrus2' into DUI-AddonsCoreLibCatUnderCorrectTreeAlt
Local build fix
Shortened local variables are renamed to full versions (e.g. xyzEle -> xyzElement)
OnExecuted made internal
BrowserRootCategories (AddonRootCategories) collection is saved in CategoryBuilder
RemoveEmptyCategories made void
Merge pull request #132 from vmoyseenko/DUI-AddonsCoreLibCatUnderCorrectTreeAlt

CustomNode should be always added to AddonsTreeView - alternative implementation