Band Image Uploader created and setup

[#47962741]
Adds new Model BandImage linked to Band model and BandImageUploader

[#47962741]
Adds controller and views for BandImage

[#47962741]
I18n added - New version in Uploader - Seed for bands' default images - Adds band thumb image in show page

[#47962741]
Adds shared sidebar in devise views

[#47962741]
Tests added for BandImage and BandImageUploader - Other tests fixed

[#47962741]
Merge pull request #16 from WilfriedDeluche/bands-images-47962741

Bands images 47962741