objectRegistry can leak memory

As discussed with @Mattijs - since all HashTable operations are visible through objectRegistry, anything that removes entries using the HashTable methods can leak memory if the object is owned by the registry.

mentioned in commit 47493f50

• checkOutByName() could be a rather convenient way to purge old, unwanted fields.

@andy - related to EP829 (will speak tomorrow)

odd-looking use of store() in basicThermo

mentioned in commit 1dea317a

mentioned in commit 91bf6288

Instead of checkOutByName() or equivalent, just corrected the handling of erase() to ensure that it doesn't leak memory. This provides the same functionality with an existing method name and plugs potential memory leaks.

mentioned in commit cb0a2636

mentioned in issue #613 (closed)