add geoip + default pipeline definitions

[graphaelli]

Adds two new pipeline definitions without changing the existing apm_user_agent:

• apm_user_geo - only GeoIP resolution of client.ip to client.geo
• apm - both apm_user_agent and apm_user_geo

updates the default pipeline suggested in apm-server.yml

closes #1283

[jalvz]

this could do with some integration test if not too complicated

[simitt]

I agree, fwiw there are already some pipeline registration and pipeline setup system tests that you could extend.