app: replaced Eloquent with Model for several model classes

This was done as part of getting Hardik's changes for #615 in master.

Eloquent and Model are essentially the same thing so that shouldn't change much.  More detail is at:
https://laracasts.com/discuss/channels/eloquent/models-vs-classes

A few other changes were made in the models such as using hasMany in 1-N relationships.  The belongsToMany is mainly for M-N relationships.

Author: joshi1983

app/app/Country.php

@@ -11,7 +11,6 @@
 class Country extends Model
 {
     protected $table = 'country';
-    protected $fillable = ["name"
-    ];
+    protected $fillable = ["name"];
     public $timestamps = false;
 }

app/app/DataSource.php

@@ -2,9 +2,9 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 
-class DataSource extends Eloquent
+class DataSource extends Model
 {
     protected $fillable = [
         'name', 'description',
@@ -18,6 +18,6 @@ class DataSource extends Eloquent
      */
     public function locations()
     {
-        return $this->belongsToMany('App\Location');
+        return $this->hasMany(Location::class, 'data_source_id');
     }
 }

app/app/Image.php

@@ -2,10 +2,10 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 use Webpatser\Uuid\Uuid;
 
-class Image extends Eloquent
+class Image extends Model
 {
     protected $fillable = [
         'id', 'location_id', 'raw_data',

app/app/Location.php

@@ -2,21 +2,23 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 use DB;
 use Webpatser\Uuid\Uuid;
 
-class Location extends Eloquent
+class Location extends Model
 {
     protected $fillable = [
         'name', 'phone_number', 'longitude', 'latitude', 'owner_user_id',
         'data_source_id', 'universal_rating', 'creator_user_id', 'ratings_cache'
     ];
+
     public $timestamps = false;
 
     protected $casts = [
         'ratings_cache' => 'array'
     ];
+
     protected $table = 'location';
     /**
      * Indicates if the IDs are auto-incrementing.
@@ -57,7 +59,7 @@ public function personalizedRatings()
 
     public function comments()
     {
-        return $this->hasMany('App\ReviewComment');
+        return $this->hasMany(ReviewComment::class);
     }
 
     public function locationGroup()

app/app/LocationGroup.php

@@ -2,9 +2,9 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 
-class LocationGroup extends Eloquent
+class LocationGroup extends Model
 {
     protected $fillable = [
         'name',

app/app/LocationLocationTag.php

@@ -2,10 +2,10 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 use Webpatser\Uuid\Uuid;
 
-class LocationLocationTag extends Eloquent
+class LocationLocationTag extends Model
 {
     protected $fillable = [
         'location_id', 'location_tag_id',

app/app/LocationTag.php

@@ -2,9 +2,9 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 
-class LocationTag extends Eloquent
+class LocationTag extends Model
 {
     protected $fillable = [
         'name', 'description',

app/app/Question.php

@@ -2,11 +2,11 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 use DB;
 use App\Location;
 
-class Question extends Eloquent
+class Question extends Model
 {
     protected $fillable = [
         'question_html',

app/app/QuestionCategory.php

@@ -2,9 +2,9 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 
-class QuestionCategory extends Eloquent
+class QuestionCategory extends Model
 {
     protected $fillable = [
         'id', 'name',

app/app/Region.php

@@ -2,10 +2,10 @@
 
 namespace App;
 
-use Eloquent;
+use Illuminate\Database\Eloquent\Model;
 use DB;
 
-class Region extends Eloquent
+class Region extends Model
 {
     protected $fillable = [
         'name', 'country_id',