New classes are created
SearchCategory can't be expanded
Removed empty lines
Used #if for comments
Fixed SearchModelTests
Some methods are made as Private
splitCat[0] is refactored to rootCategoryName
Node moved from constructor of SearchCategory
Added CreateInstance for SearchMemberGroup
Returned original signature of Search
Merge pull request #93 from vmoyseenko/DUI-SearchDataStructure

SearchRootCategories collection is introduced