Simpler parsing of YAML, and allow return of DotNotation object

[jcrivenaes]

This is related to #88

Make a parser on the following pattern

from fmu.config import load_fmuconfig

cfg = load_fmuconfig()   # defaulted to read ../../fmuconfig/output/global_variables.yml

The return should be an object where both the current dict notation is allowed, but also allow a new "dot" notation.

[jcrivenaes]

Postpone this, see it in relaton with #70 possibly