update FCS to 0.0.28

unignore LanguageService test for named DU fields
Merge pull request #110 from vasily-kirichenko/update-fcs-to-0.0.28

update FCS to 0.0.28
Merge pull request #107 from vasily-kirichenko/master

Optimized: RenameCommandFilter does not update its state if symbol under caret is not changed
add document events throttling