added comments, minor refactor

bindings/java/src/org/sleuthkit/datamodel/Account.java

...va/src/org/sleuthkit/datamodel/AccountDeviceInstance.java

...java/src/org/sleuthkit/datamodel/AccountFileInstance.java

...s/java/src/org/sleuthkit/datamodel/AccountTypeFilter.java

...va/src/org/sleuthkit/datamodel/CommunicationsManager.java

...ngs/java/src/org/sleuthkit/datamodel/DateRangeFilter.java

bindings/java/src/org/sleuthkit/datamodel/DeviceFilter.java

tsk/auto/db_postgresql.cpp