update LDAP setting descriptions in the "external systems" UI

The description for each of Batch Size, Count Limit, Time Limit, and Timeout is..

"optional (note, time limit is for search operations, timeout is for connection timeouts), most of these default to ldaptive defaults. times are in millis"

I think it would be more helpful to describe what each of those limits are for (and house batch size / count limit are different than "paged result size")