Todo: Clean up overly complex exception definition in dbAccess.h

[Rick Stovall]

As a general rule, exceptions inherited from nrtb::base_exception do not need to have anything overidden when they are declared/defined. For example, the following would be fine in a class header:

public:
    // Thrown by my_method() in cases of unexpected error.
   class my_method_exception: public nrtb::base_exception {};

This is cleaner and easier to read than the exception class declarations currently present in dbAccess.

[George Jordan (gsjordanc)]

Fixes and adjustments made in version 38.