NETCONF edit-config implementation should allow for passing <rpc-error> to caller

In the Interface NetconfSession.java the edit-config method(s) only pass back a boolean in response
true - means rpc-reply with <ok> was received
false - means rpc-reply with one or more <rpc-error> was receieved instead.

There could be any reason for these <rpc-error>(s) and the reason is lost by narrowing the reply to just a boolean.

For instance if the reason is "access-denied" I want to handle this differently at the user level than if it's a validation error.

This also applies to any other command that can return an error e.g. doWrappedRpc, delete-config etc.

Also the description of editConfig() method's in NetconfSession.java is incorrect - it does not "Retrives part of the specified configuration based on the filterSchema" - a copy and paste oversight from get-config I think