Create function for Probability calculation and normal distribution

See merge request !76

# Conflicts:
#	app/build.gradle

# Conflicts:
#	app/build.gradle
#	app/src/main/AndroidManifest.xml

# Conflicts:
#	app/build.gradle
#	app/src/androidTest/java/com/elearning/probabilityandstatisticsanalyserandeducator/WelcomeTest.java
#	app/src/androidTest/java/com/elearning/probabilityandstatisticsanalyserandeducator/adaptiveLearning/StartingScreenTest.java

Recommendations are working

See merge request !75

Create the testcases for Descriptive statics ,standard deviation and probability distribution calculation

Course handler function completed with Video Controller

See merge request !74