merge commit for IDE.md (IntelliJ IDEA section)

IDE.md file (IntelliJ IDEA section) updated

The information was updated and the following procedures were added:
- Creating a new Play application
- Importing an existing Play project
- Running/Debugging Play application

IDE.md (IntelliJ IDEA section) updated

Minor changes suggested by Rich Dougherty were included.
Merge pull request #2722 from elenakozlova/2.2.x

IDE.md file (IntelliJ IDEA section) updated