GEOMESA-144 Set temporal index variable by default if not selected by user

GEOMESA-144,GEOMESA-140
    
    GEOMESA-140 Warn users about missing temporal component of index
    This commit adds a warning when a user neglects to properly set SF_PROPERTY_START_TIME in the UserData. Such a mistake is non-fatal, but does impact performance.
    
    GEOMESA-144 Set temporal index variable by default if not selected by user
    This commit will set SF_PROPERTY_START_TIME for the user if only one time attribute is present in the SimpleFeatureType, and emit a notification to this effect.
I'd see if you could use string interpolation with this. E.g....
``` 
  |However, the following attribute(s) could be used in GeoMesa's temporal index:
   |${matches.mkString("\n", "\n", "\n")}
   |Please note that while queries on ...
```