Updated Tracker
Added basic implementation for Google Analytics tracker
API updated
Comments addressed.
Merge pull request #669 from anserran/ga

Basic implementation of user tracking system (using Google Analytics)
    Added ConversationSystem, DialogueSystem

    - ConversationSystem processes a TalkComponent, which is added by
      TriggerConversation effects. They are display-independent.

    - DialogueComponent processes DialogComponents, which can specify
      callbacks. Currently they all have the same style; this will
      be addressed in later commits.
Added ConversationDemo

Click on dialogues to choose / dismiss them.
Add a components.dialogue package, systems.dialogues package

Since there are now two types of dialogues (menu and line)
Cleaner, call-back free conversations.

Conversation advancement is done via polling. Removed logging.
Small bugfix in Selection
Merge pull request #664 from manuel-freire/conversation-support

Conversation support
Small default FocusItemStyle improvements.
Adds necessary actions and tests.
FocusItemList and LinearLayout improvements.
Renamed FramesTimelineTest to AnimationEditorTest.
Adds AnimationEditor.
Convenence methods and attributes.
FrameWidget refactoring (duplicate, delete, correctly managing the time...).
FramesTimeline refactoring. WOrks with selection, undo/redo, drag and drop...
Adds PreviewView, a view that holds an FramesComponent and displays/updates it when the model changes.