Improve configurability of EmbeddedDatabaseBuilder

This commit improves the configurability of EmbeddedDatabaseBuilder by
exposing the following new configuration methods.

 - setDataSourceFactory(DataSourceFactory)
 - addScripts(String...)
 - setScriptEncoding(String)
 - setSeparator(String)
 - setCommentPrefix(String)
 - setBlockCommentStartDelimiter(String)
 - setBlockCommentEndDelimiter(String)
 - continueOnError(boolean)
 - ignoreFailedDrops(boolean)

If more fine grained control over the configuration of the embedded
database is required, users are recommended to use
EmbeddedDatabaseFactory with a ResourceDatabasePopulator and forego use
of the builder.

Issue: SPR-11410

spring-jdbc/src/test/resources/org/springframework/jdbc/datasource/embedded/db-schema-block-comments.sql

@@ -0,0 +1,9 @@
+{*
+	these are custom block comments
+*}
+drop table T_TEST if exists;
+
+{*
+	these are custom block comments
+*}
+create table T_TEST (NAME varchar(50) not null);

spring-jdbc/src/test/resources/org/springframework/jdbc/datasource/embedded/db-schema-custom-comments.sql

@@ -0,0 +1,5 @@
+~ Failed DROP can be ignored if necessary 
+drop table T_TEST if exists;
+
+~ Create the test table
+create table T_TEST (NAME varchar(50) not null);

spring-jdbc/src/test/resources/org/springframework/jdbc/datasource/embedded/db-schema-derby.sql

@@ -1 +0,0 @@
-create table T_TEST (NAME varchar(50) not null);