Finalizing the implementation of file registration

Adding the file system check in Linux(can be enabled from the config
file)
Adding a more options to the config file
Writing the README

file_hasher.c

@@ -82,7 +82,7 @@ int main(int argc, char **argv) {
   // Logical threads = CPU cores * 2
   uint32_t cpu_threads = cpu_cores * 2;
 
-#if MULTI_THREADED
+#if MULTI_THREADING
   uint32_t num_scan_threads = cpu_threads;
   uint32_t num_hash_threads = cpu_threads;