Add a Light colored Theme

[GrazianoCapelli]

A dark theme is a Nightmare to use in bright Environments. I propose to implement a light Theme to improve the readability in these conditions. The user should have the possibility to switch between light and dark Theme during the usage.

Here a list of tasks:

• [ ] Add a ListPreference "Color Theme" with 2 items: Dark and Light. The default theme would be the Dark one
• [ ] Add the 2 colors file for Dark and Light theme (Theme.AppCompat.DayNight). We should start using the complementary colors, and the red instead the yellow (as shown in the screenshot here below)

Here a first UI mockup of the light theme, just to start the implementation:

No translations are needed for the 3 new strings, we manage them on Crowdin. Please don't push translated strings, but only the american english one (strings.xml). If you want to see an example of how we would like to implement the dark/light theme, you can look at GPS Logger. We could evaluate to add a third item to theme preference, to follow the "System" settings.

PS: no third party libraries to implement the theme, we should use the standard Android way (like GPS Logger).

[Jenish-1235]

I can add light theme as well as any other color theme support in app. You can assign this issue to me.

[GrazianoCapelli]

I updated the header comment in order to better describe what we would like to implement. Please read it carefully and, if you think that it is good for you, give me a feedback. I would be be glad to assign this issue to you.

If you work on more than 1 issue, please use a different branch for each one. You can read the CONTRIBUTING.md file.

PS: Alternative UI mockups are harmly welcome.

[Jenish-1235]

Yes, definitely. I will be using separate branches for separate issues. I can accomplish this task. You can assign this to me.