Add preferences

[filol]

• Add CheckBox
• Add Switch
• Update gradle
• Change deprecated function inside build.gradle
• Update README
• Update DemoApp for testing preferences items
• Add french translation

77

[filol]

I made the corrections. The only details I did not manage to do with Linear layout is to center the switch and the checkbox. You'll see when you put a checkbox under a switch that they are not centered

[daniel-stoneuk]

Thanks! I'll check it out and merge onto master branch later

[filol]

I forget some error in the README. See PR #86