Add SdFs::format(), improve "const correctness", zip doc

Change SD_FAT_VERSION from string to integer

Timestamp fix, edit src for cplint errors

Add time st

Fix cache bug for FAT16/FAT32

Fix open bug

Add null pointer checks

Use fcntl.h for ESP32

Fix FatFile::printName() bug

Support for SdFatLite library.

Add openCwd(), fix library.properties for Particle