fix(0.4/2017-05-29--test_image.xml): use type-aware attribute to fix migration on PostgreSQL.

The failure was:
MigrationFailedException: Migration failed for change set classpath:/liquibase/version/0.4/2017-05-29--test_image.xml::add-test-image::php-coder:
Reason: liquibase.exception.DatabaseException: org.postgresql.util.PSQLException:
ERROR: column "image_id" is of type integer but expression is of type character varying
Hint: You will need to rewrite or cast the expression.

Addressed to #1034

Author: php-coder

src/main/resources/liquibase/version/0.4/2017-05-29--test_image.xml

@@ -8,7 +8,7 @@
 	<changeSet id="add-test-image" author="php-coder" context="test-data">
 
 		<insert tableName="images_data">
-			<column name="image_id" value="1" />
+			<column name="image_id" valueNumeric="1" />
 			<column name="content" valueBlobFile="/test/test.png" />
 		</insert>