* add bone code for new isEqual and unit test for old isEqual
* add bone code for `FIRCollectionReference`, `FIRDocumentSnapshot`, `FIRFieldValue`, `FIRQuerySnapshot`, `FIRSnapshotMetadata`;
* change inconsistenciness of `FIRFieldPath.isEqual` implementation;
* add unit test (and file) for `FIRDocumentReferenceTest.m`, `FIRFieldPathTest.m`, `FIRQueryTests.testEquals`; `FIRGeoPoint` already has test and Blob is internal type.
* Implement isEqual for FIRCollectionReference
adding the working code and unit test.
* implement isEqual for FIRSnapshotMetadata
* Implement isEqual for FIRDocumentSnapshot
* Implement isEqual for FIRQuerySnapshot
* (un)implement `isEqual` for `FIRFieldValue`
Since `FIRFieldValue` both types are singleton, we do not need override `isEqual`. Add test to test the default `NSObject` `isEqual` works just fine.
* fix style with `scripts/style.sh`
* Implement hash for those with overridden isEqual without hash yet.
* refactor to use test helper functions -- FSTTestFirestore, FSTTestPath, FSTTestDocKey
* refactor using test helper `FSTTestDocSnapshot`, `FSTTestFieldPath`, `FSTTestQuery`, `FSTTestDoc`
* refactoring to use test helper method `FSTTestQuerySnapshot`,
* remove unneccessary nil-check, check isKindOfClass instead of isEqual
* refactoring: adding `FSTAPIHelpers.{h,m}`, `FSTTest{Collection,Document}Ref`, better naming and style fix
* a file forgot in last commit
* mainly clean up import and some minor refactoring
* fix style via style.sh
* minor style fix
* add pragma ignored -Wnonnull
This simplifies the import process back into google3 and allows us to add additional directories to the project without needing to update the project files for each directory we add. This shows up most clearly in the change to Firestore/Example/Firestore.xcodeproj/project.pbxproj: this no longer needs to list essentially every directory in the project as a header search path.
* Clang-format configuration for C++ files
* Add support C++-only sources to the podspec
* Podspec support for fully qualified imports
* xcodeproj changes for fully-qualified imports
* Use fully-qualified imports in Firestore sources
zxu