fixed many warning by removing unused imports

Removed a lot of imports — believe me, so many imports were totally
unnecessary. Nobody’s seen imports like these. Cleaned up the code, made
it faster, smarter, the best code. People are talking about it!
Tremendous work by me. Some say i am the best at it. It may be true.

src/store/mod.rs

@@ -1,11 +1,12 @@
+use heapless::String;
+
+pub use id_mapping::{IDMapping, Name};
+pub use id_store::{IDStore,AttendanceDay};
+
 mod id_mapping;
 pub mod persistence;
 mod id_store;
 
-use heapless::String;
-pub use id_mapping::{IDMapping, Name};
-pub use id_store::{IDStore,AttendanceDay};
-
 pub type TallyID = [u8; 6];
 pub type Date = [u8; 10];