* add abstractPhpCodegen
* This base class should provide common functions to PHP-related generators so that the same enhancements or bug fixes can be applied to all clients.
Most source be moved from the PhpClientCodegen.
* change Lumen codegen to use the AbstractPhpCodegen
* remove the composerVendorName/composerProjectName. modify the LumenServerOptionsTest for unit test
* add context path
* reserve the apiDocPath and modelDocPath
* add the templateDir for lumen
