jaeger_remote needs clarity

[marcalff]

The yaml node for jaeger_remote currently has the following schema:

• an optional endpoint property
• an optional interval property
• an optional initial_sampler property

The endpoint should probably be required.

The interval should be required, or a default value should be defined. The unit for this value should be defined as well.

The initial_sampler should be required, or a default behavior should be defined (always_off, always_on ?).

This is blocking for the 1.0.0 release, as any changes here (optional property that becomes mandatory) will be a breaking change.

Blocking for #161

[marcalff]

Also, jaeger_remote is not covered in examples.