firebase-ios-sdk

FieldValue and DocumentReference codable support. (#3231)

* working serverTimestamp

* working FieldValue. Still need: document ref and ability to Eq of FieldValue

* DocumentReference implemented and testing works

* clean up header search path

* improving FieldValue enum comments

* run through formatting

* addressing comments

* formatted with swiftformat 0.35.7

* add missing bool->BOOL change

* undo unintended swift version change

* remove unwanted proj file change