Draft: API: remove UniqueResult, lower-case at, size for ResultSet

Summary

• Remove UniqueResult
• At and Size are lower-case now (ResultSet, MultiResultSet)

include/ccaosdb.h

@@ -249,8 +249,12 @@ int caosdb_connection_connection_create_transaction(
   caosdb_transaction_transaction *out);
 int caosdb_transaction_transaction_retrieve_by_id(
   caosdb_transaction_transaction *transaction, const char *id);
+// TODO(fspreck) retrieve_by_ids what do we do about iterators in Extern C?  Is
+// this even a problem?
 int caosdb_transaction_transaction_execute(
   caosdb_transaction_transaction *transaction);
+// TODO(fspreck) execute_asynchronously may be added as a separate
+// function once we actually support asynchronous execution.
 
 typedef struct {
   void *wrapped_result_set;