Please add output of element name when there is an error

[hlindberg]

When getting an error like this:

panic: reflect: call of reflect.Value.SetFloat on int32 Value [recovered]
	panic: reflect: call of reflect.Value.SetFloat on int32 Value

When calling vf.FromValue(v, target) it is time consuming to figure out where the problem is when there are multiple int32 values in the target structure.
Suggest adding the name of the type/member that it is failing on in the error message. There should probably be a general catch that amends all error messages.

[hlindberg]

There is a similar problem when the yaml file does not parse ok. For example:

henrik$ lookup mykey --explain
Error: yaml: line 2: found unexpected end of stream
&{0xc0000bc0c0} yaml: line 2: found unexpected end of stream

That error comes from one yaml data file among 50 or so...