Refactor database drivers

README.md

 Edit the following lines in the bottom of the file "api.php":
 
 ```
-$api = new MySQL_CRUD_API(array(
-	'username'=>'xxx',
+$api = new PHP_CRUD_API(array(
+  'username'=>'xxx',
 	'password'=>'xxx',
-	'database'=>'xxx'
+	'database'=>'xxx',
 ));
 $api->executeCommand();
 ```
 These are all the configuration options and their default values:
 
 ```
-$api = new MySQL_CRUD_API(array(
-	'username=>'root'
+$api = new PHP_CRUD_API(array(
+  'dbengine=>'MySQL',
+  'username=>'root',
 	'password=>null,
 	'database=>false,
 // for connectivity (defaults to localhost):
 	'input_sanitizer'=>function($cmd,$db,$tab,$col,$typ,$val) { return $val; },
 	'input_validator'=>function($cmd,$db,$tab,$col,$typ,$val,$ctx) { return true; },
 // dependencies (added for unit testing):
-	'db'=>null,
-	'method'=>$_SERVER['REQUEST_METHOD'],
+  'db'=>null,
+  'method'=>$_SERVER['REQUEST_METHOD'],
 	'request'=>$_SERVER['PATH_INFO'],
 	'get'=>$_GET,
 	'post'=>'php://input',
 $
 ```
 
-NB: You MUST use an empty database as a desctructive database fixture ('blog.mysql') is loaded.
+NB: You MUST use an empty database as a desctructive database fixture ('blog_mysql.sql') is loaded.
 
 ### SQL server on Windows:
 
 C:\mysql-crud-api-master>
 ```
 
-NB: You MUST use an empty database as a desctructive database fixture ('blog.mssql') is loaded.
+NB: You MUST use an empty database as a desctructive database fixture ('blog_sqlserver.sql') is loaded.
 
 ### PostgreSQL on Linux
 
 $
 ```
 
-NB: You MUST use an empty database as a desctructive database fixture ('blog.pgsql') is loaded.
+NB: You MUST use an empty database as a desctructive database fixture ('blog_postgresql.sql') is loaded.
 
 ## Pretty URL
 

api.php

 // uncomment the lines below when running in stand-alone mode:
 
 // $api = new PHP_CRUD_API(array(
+// 	'dbengine'=>'MySQL',
 // 	'hostname'=>'localhost',
 //	'username'=>'xxx',
 //	'password'=>'xxx',
 // ));
 // $api->executeCommand();
 
-// For Microsoft SQL Server use:
+// For Microsoft SQL Server 2012 use:
 
 // $api = new PHP_CRUD_API(array(
+// 	'dbengine'=>'SQLServer',
 // 	'hostname'=>'(local)',
 // 	'username'=>'',
 // 	'password'=>'',
 // ));
 // $api->executeCommand();
 
-// For PostgreSQL use:
+// For PostgreSQL 9 use:
 
 // $api = new PHP_CRUD_API(array(
+// 	'dbengine'=>'PostgreSQL',
 // 	'hostname'=>'localhost',
 // 	'username'=>'xxx',
 // 	'password'=>'xxx',