[PHP] Refactor php client generator (#504)

* Extends AbstractPhpCodegen instead of DefaultCodegen

* Remove fully duplicated methods with AbstractPhpCodegen

* Remove duplicated properties with AbstractPhpCodegen

* Remove duplicated codes in constructor with AbstractPhpCodegen

* Add typeMapping "date". Moved from PhpClientCodegen

refs: 3c34c0b377 (diff-f1801ef05a7926bf394c90f44ae4ab3dL132)

* Remove duplicated codes in processOpts()

* Remove unnecessary 'implements'

* Remove unnecessary method override

* Use setter

* Merge getTypeDeclaration() into AbstractPhpCodegen

* Merge processOpts() into AbstractPhpCodegen

refs:
* 296e6d3db4 (diff-f1801ef05a7926bf394c90f44ae4ab3dL139)
* 296e6d3db4 (diff-f1801ef05a7926bf394c90f44ae4ab3dL147)
* 296e6d3db4 (diff-f1801ef05a7926bf394c90f44ae4ab3dL153)

* tweak

* Optimize IF statement

* Remove duplicated methods

* Merge setParameterExampleValue() into AbstractPhpCodegen

* Merge toEnumVarName() into AbstractPhpCodegen

* Merge toEnumName() into AbstractPhpCodegen

* Merge escapeUnsafeCharacters() into AbstractPhpCodegen

* Merge postProcessOperationsWithModels() into AbstractPhpCodegen

* tweak

* Recover missing method

refs: 2ad0f6f7d4 (diff-f1801ef05a7926bf394c90f44ae4ab3dL91)

* Tweak test case

refs: 4e7b7afc1a

* Remove unnecessary 'import'

* Update lumen and ze-ph samples

- ./bin/php-lumen-petstore-server.sh > /dev/null 2>&1
- ./bin/php-ze-ph-petstore-server.sh > /dev/null 2>&1

* Update slim samples

* Fix script name

* Update silex samples

* Update kotlin-server

samples/server/petstore/php-slim/lib/Model/Capitalization.php

@@ -24,7 +24,7 @@ class Capitalization {
     /** @var string $sCAETHFlowPoints */
     private $sCAETHFlowPoints;
 
-    /** @var string $aTTNAME Name of the pet */
+    /** @var string $aTTNAME Name of the pet*/
     private $aTTNAME;
 
 }