Improve example's button texts
Add installer script and data.

To create installers the Qt installer-framework is needed.
Currently building installers is only tested on windows.
Merge pull request #179 from gladhorn/installer

Installer
Merge pull request #182 from nierob/master

EnginioModel fixes
Fix documentation warnings.
Use consistent naming convention.

Rename all local EnginioReply pointers to "ereply".
Fix crashes in EnginioModel when EnginioClient is not set.
Mark some methods with Q_REQUIRED_RESULT

All methods without side effects can be marked with Q_REQUIRED_RESULT
so compiler warn if result is not used.