Release new version 1.4.2

This issue should be cloned anytime we are going to release a new version pointing to the new version in the Fix Version/s field.

Task to be performed every time we are going to release a new version:

• Bump version numbers (config.json and config.xml)
• Disable debugging in config.json
• Update the local_moodlemobileapp plugin with new strings in moodle.org/plugins
• Update language strings and pack from AMOS
• Create a TAG in github with the version number
• Update Developers Documentation
• Update User Documentation
• QA tests
• Build the app for Android
• Build the app for iPhone
• Release the app in Play Store
• Release the app in Apple app Store
• Forum and twitter announcements