Add settings for features

Add a new tab in the settings: Features.

• Position: after General.
• The contents is a list of switches for every feature.
• The default state is the one from Options.

When changing a state, the preference is written into the local configuration file (updated or may need to be created):

[DEFAULT]
env = features

[features]
feature.name = true/false

The local config part needs tests to be sure old parameters are not lost, and that feature on/off is well handled.

—

Why Write to the Local Config File?

1. Because this is the only way to persist preferences about features. Drive will load the file and adapt its components based on what it will find.
2. Because saving the feature state into the database would make the configuration handling even more hard to follow and handle: just keep it as complex as it already is.