ERT-743: EclSUm.get_interp() works for days=0
ERT-743: Special case for interpolation at start

In general the time intervals are halfopen to the upper end when mapping
from true sim_time to a ministep block, but there is a special case when
interpolating at the the start of the simulation.
Merge pull request #595 from joakim-hove/ERT-743-eclsum-interp

Ert 743 eclsum interp
ERT-745: Removed debug printf() messages
ERT-745: Added function time_map_fscanf()
ERT-745: Added TimeMap.__setitem__()
ERT-745: Added time_map lookup functions
ERT-745: Using time_map instead of history

1. Introduces the config option TIME_MAP which can be used to load a
   time map manually from a formatted file.

2. The various obs_vector_() initializer functions use a time_map
   instance instead of a history instance to map between dates/days
   and report steps.

The purpose of this commit is to facilitate updates also in situations
where we do not have either an ECLIPSE refcase or a Schedule file.
ERT-745: model_config will check external_time_map
ERT-745: Disable updates based on enkf_obs_have_obs()
ERT-745: Using enkf_obs_have_obs()
ERT-745: Will copy case if no update performed
ERT-745: Add protection against alias -> alias
ERT-745: Added workflow_is_instance()
ERT-745: Added internal alias_map to workflow_list