Speed increase on startup in presence of many RelTypes

On bulk RelType import that happens on startup, instead of using the
 COW map and insert one by one, store all derived data in local Maps
 and addAll() those to the COW in one operation. Equally thread safe
 and much faster.

There are stores that take more than 2 minutes to load because of 50k+ reltypes. That many COW map put operations take a long time because of copy and GC strain. This solves such issues.