Change level messages, add question count

Update the current level messages to be more motivating.
Add a question count directive with the text 'x of y questions'.
1- Refactor multiple choice question types directives. This includes:
    1.1- Add 'ng-class' to letter button, when the 'selected' property change it affects directly to add or remove the required class.
    1.2- Finish to remove/reduce jQuery selectors. In order to avoid too many access to the DOM.
    1.3- Add 'ng-click' method to each row on each directive. This is how it executes now the logic to select a choice.

2- Remove old services dedicated to handle multiple choice directives.
3- Remove old jQuery 'existsInArray' service.(The logic related to this service is now using lodash).
4- Remove un unused 'easyPieChart' directive.(This wont be needed since we removed the old way to show the score prediction).
5- Add missing call to 'loadQuestionSet()'.

*(2)- Since we work directly with scope value, maybe will more readable keep the directive code inside the link function instead of have it into a service(this can be evaluate it later).
Merge pull request #26 from mlopez-firstfactory/master

Refactor the input number validation. Extract repeated code in the practice service into a common method, add the repeat tag filter.
Add margin style for 'get your score prediction' button.
Finish logic to get score prediction url for each track.
Improve html 'get your score prediction' button.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	angular_webApp/src/app/practiceGame/common/practice.directive.js
	angular_webApp/src/app/practiceGame/custom-practice/customPractice.ctrl.js
	angular_webApp/src/app/practiceGame/custom-practice/customPractice.tpl.html