plot_class_tabs function not displaying correctly in Google Colab environment

[karolzak]

Noticed that there are 2 issues with using ipyplot inside Google Colab environment (probably in similar environments like Azure Notebooks or Kaggle as well?):

1. HTML displays broken image file links when trying to plot images directly from local filesystem using string file paths - seems like there's some problem with relative paths for HTML under Google Colab notebooks
   

2. plot_class_tabs styling is completely broken which means that bootstrap js package is missing
   

Fix propositions:

1. Add force_b64 param to all the functions which would load file from local file system to the memory and convert into base64 format and inject it directly into html

2. Simplify HTML layout to get rid of any external JS libs and just use basic HTML + CSS