Rohit Kaushik authored Jun 16, 2017 and Georges Basile Stavracas Neto committed Jul 13, 2017

Since Todoist uses an integer mapped to hex code for list color,
but To Do uses GdkRGBA we need function that will do the necessary
conversion from one to other.
This patch add following method:
  1)convert_color_code: This converts todoist supported int code to
    To Do  supported GdkRGBA color.

  2)get_color_code_index: This returns index for To Do supported GdkRGBA
    color which maps correctly to todoist color codes (hex).

  3)optimized_eucledian_color_distance: Required by 2nd method to find
    To Do color closed to todoist predifined color codes.

https://bugzilla.gnome.org/show_bug.cgi?id=772278