Support 'theme files'

Hi all,

This is more of a feature request than bug report.

Recently I’ve been looking at the interesting base16 project, which already supports various IDEs and software, and was thinking I could port these themes to Spyder.

However the way Spyder handles color schemes is quite inconvenient. If I understand correctly all themes are store in a subsection of spyder.ini? Also, while the interface created by @goanpeca (https://github.com/spyder-ide/spyder/pull/2861) in Spyder 3 is great, when creating many themes it is usually faster to edit a text file rather than the current gui-based method.

I wonder if it wouldn’t be more practical to have single theme files instead, which would be stored in a given themes folder. Spyder could scan the contents of this folder on startup. This of course would be perfectly compatible with the current GUI method, but would have the benefit of making importing 3rd party themes very easy.

(PS: you can visualise the many base16 color schemes here: http://chriskempson.github.io/base16/)

[ccordoba12]

This doesn’t require GUI work on your side. Just

1. Move the theme definitions from spyder/config/main.py to spyder/themes as json files (each theme in a file).
2. Code a function that reads those files, transforms them to dictionaries and adds them back to spyder/config/main.py.

[goanpeca]

@mariacamilaremolinagutierrez this work is related to the theming functionality we want to have so please work on this one 😃

Lets have an open mind already about themes that include both the application look and the editor look.