Replace hardcoded directory "src/" with constant APP_DIR

[fabian-mcfly]

CakePHP always uses the APP_DIR that allows the developer to chang the directoy from src/ to something different.
In /src/Shell/AnnotationsShell.php in line 77/79 and 241/242 the path src should not be hardcoded but use APP_DIR instead, in case it's not a Plugin.

Line 77 should be: $path = ($plugin ? PluginPath::get($plugin) . 'src' : ROOT . DS . APP_DIR) . DS;
Remove Lines 78 & 79

Line 241 should look the same: $path = ($plugin ? PluginPath::get($plugin) . 'src' : ROOT . DS . APP_DIR) . DS;
Remove Line 242

Line 608 also has src/ hardcoded and should look like this:
$this->warn('You need to create AppView.phpfirst in' . APP_DIR . DS . 'View' . DS . '.');

For the remaining src in Line 77 & 241, the PluginPath::get($plugin) should use CakePHPs Plugin::classPath instead (but not for every usage of PluginPath::get($plugin)) . This way you wouldn't need to add the src yourself.

Disclaimer: Sorry for not forking and creating a pull request but I'm not that familiar with Github and don't want to make a mistake here.

[dereuromark]

Feel free to make a PR here.

[dereuromark]

Is #237 what you had in mind?