Fixes #294 - get to zero warnings

[BillBarnhill]

• [symbol.rs] extract score compute into fn compute_match_score
• [symbol.rs] extract getting SymbolInformation from a Referenceable to pub Vault::to_symbol_information
• [vault/mod.rs] add non-pub find_range, used by Vault::to_symbol_information
• [vault/mod.rs] add pub to_symbol_information to Vault impl, with allow for deprecation and explanation [vault/mod.rs] fix a couple of hidden lifetimes
• [symbol.rs] modify workspace_symbol to reflect above refactorings [symbol.rs] fix deprecated warning by adding allow macro ot map_to_lsp_tree, with explanation