optimize Find all references for file scoped symbols

add a test for "byref" type colorization
remove unused type
fixed: FindReferencesFilter does not work for external symbols in standalone files
fixed: wrong ProjectOptions is used for fsx files
Merge pull request #364 from vasily-kirichenko/optimize-find-all-refs-for-file-scoped-symbols

optimize Find all references for file scoped symbols
Merge remote-tracking branch 'upstream/master'