Changed io_type to i_o_type in the foreign key definitions of person targets

and account classes.

database/migrations/2018_09_07_090338_create_person_targets_table.php

@@ -32,7 +32,7 @@ class CreatePersonTargetsTable extends Migration
             // receivable. A payable is of type 'expediture' and a receivable is
             // of type 'income'.
             $table->integer('io_type')->unsigned();
-            $table->foreign('io_type')->references('id')->on('io_types')
+            $table->foreign('io_type')->references('id')->on('i_o_types')
                   ->onDelete('no action');
 
             // A reference text which describes the target

database/migrations/2018_09_07_090452_create_account_classes_table.php

@@ -21,7 +21,7 @@ class CreateAccountClassesTable extends Migration
 
             // The type of the account class.
             $table->integer('io_type')->unsigned();
-            $table->foreign('io_type')->references('id')->on('io_types')
+            $table->foreign('io_type')->references('id')->on('i_o_types')
                   ->onDelete('no action');
             
             // The scope of the account class.