Fix for #1677: show topics with exercises as available.
Add tests for validating topic and video availability.
 Issue 1476 Don't show Dropdown box if only one language is there
updated .gitignore
Added a pop-up window to confirm before deleting the videos
Typo Corrected
made User Interface and Internationalization changes
removed cross sign from title bar
remove empty blocks
reset property by assigning null
use logical OR instead of bitwise OR
remove extra comma
remove unnecessary semicolon
simplify comparison
add missing semicolon
fix condition