fix: single-upper-case symbols are not highlighted

optimize LanguageService a bit
add more tests for GetUsesOfSymbolAtLocation
simplify checkSymbolUsage function
Merge pull request #30 from vasily-kirichenko/master

fix: single-upper-case symbols are not highlighted
Restrict symbol lookups on identifiers only

Use a line tokenizer to be able to recognize strings, comments and
compiler directives.

Fix #22.
Fix #24.
Highlight operators

Fix #26.

No longer highlight symbols if we can't find their references (e.g.
namespaces, type annotations, etc.).
Use "Highlight References" consistently throughout the solution
fixed: operators that started with '>' symbol are not highlighted
Merge pull request #35 from vasily-kirichenko/master

Fix: operators that started with '>' symbol are not highlighted
Reuse text marker from Highlighted References

Fix #21
fixed: operators containing dots are not highlighted
rename a DU case
Merge pull request #38 from vasily-kirichenko/master

Fixed: operators containing dots are not highlighted
fixed: symbols are not properly highlighted if there are operators with dots between them
add LanguageService tests
Merge pull request #40 from vasily-kirichenko/master

fixed: symbols are not properly highlighted if there are operators with ...
fixed: ident is not highlighted if it contacts with a special symbol on the right
Merge pull request #44 from vasily-kirichenko/master

fixed: ident is not highlighted if it contacts with a special symbol on the right
add Parser tests
Merge pull request #46 from vasily-kirichenko/master

add Parser tests