Another round of NEWS polishing (#1370)

* add reasoning to "return" removal

* mention old argument still works

* combine+clarify some brace_linter items, add attributions

* consistent capitalization, clarifications

* finish pass for consistent capitalizatoin

* grammar

* move object_name bullet with others; clarify cyclocomp bullet

* mention CRAN policy re: cache directory

* more consistently reference only the issue (not PR) #s

* consistent capitalization in my GH username

* missing item for any_duplicated_linter

* improve description of system_file_linter

* clarify strings_as_factors_linter, more grammar

* more quantification of package speed-ups; more clarirfication

* more removing redundant issue references; reorg bullet for get_source_expressions

* clarification, remove redundant issue refs

* move another object_name_linter bullet up

* move extraction_operator item to "features" not bugs

* trailing whitespace

* trailing whitespace

* feedback

* lead with Deprecated

* wording for object_usage