New DependencyInjector class. Refs #2819

- Provides a more flexible module initialization, leveraging the
  existing setter methods.
- Replaces the old callbacks mechanism.
Api doc: document deprecated methods. Refs #2819
ViewInterface: getCommandList() is deprecated. Refs #2819

Use Dependency Injection to replace the command pattern.
Xhtml renderer (useFile): use base URL paths. Refs #2819
Removed getCommandList() calls. Refs #2819

Applied in classes:
- Xhtml renderer
- Resource module
Framework: build DI container and PDP on each request. Refs #2819
Added deprecation warnings. Refs #2819
Framework: refactor of moduleLoader creation. Refs #2819
Removed CommandInterface. Refs #2819

Backward compatibility provided by LegacyCommandBag class.
ResponseInterface: HttpResponse implementation. Refs #2819
Deprecated AbstractRenderer::hashToDatasource. Refs #2819

Use \Nethgui\Widget\XhtmlWidget::hashToDatasource
Syslog: Use syslog() call instead of error_log().
Fix httpRedirection() for non-JS clients. Refs #2819
WIP Framework dispatch()
DI: added DependencyConsumer interface. Refs #2819
Model split. Refs #2819

Help, Menu, Notification, Resouce system modules have been refactored
to use a specific Model class.
Request: receive User as an external dependency.  Refs #2819

The User object was previously resurrected from Session.
AbstractLog : fixed empty call stack in deprecated() method.
NethPlatform: set default PhpWrapper instance.
ReadonlyView: fixed LogConsumerInterface implementation.