Handle application configuration using QSettings

[stdevCrow]

Description
We are using JSON format to save/restore configuration, while using QSettings is a better approach.

Advantages over the JSON approach

• Uses the standard configuration format for every system the application runs on.
  • Windows: System registry
  • Darwin: Property list files
  • UNIX: In absence of an standard, uses INI text files
• Creating and destroying QSettings objects is very fast
• It ensures that the location is always writable
• The location and storage format is transparent for the developer
• Each developer can save/load its own settings with two lines of code without affecting others or making a bigger implementation
• There is an equivalent QML component named Settings that allows to write and read settings directly from QML

See QSettings and Settings in Qt Docs for details

How to use it?

Read configurations when necessary:

QSettings settings;

int value1 = settings.value("cipher/someInteger").toInt();
QString value2 = settings.value("cipher/someString").toString();

And write/update configurations when necessary:

QSettings settings;

int value1 = 5;
QString value2 = "bla bla bla";
settings.setValue("cipher/someInteger", value1);
settings.setValue("cipher/someString", value2);

In the above examples, "cipher" it's just a group of properties, like a folder.
You can name your group (if any) as you want.

[olemis]

This needs be reopened so as to fix errors on Travis Windows builds