add refresh button for aesthetic embeddings
add aesthetic params to images' infotext

Problem
everytime I modified pt files in embedding_dir or hypernetwork_dir, I
need to restart webui to have the new files shown in the dropdown of
Train Tab

Solution
refactored create_refresh_button out of create_setting_component so we
can use this method to create button next to gr.Dropdowns of embedding
name and hypernetworks

Extra Modification
hypernetwork pt are now sorted in alphabetic order

made save style button not die when you cancel

Changed the hidden element class name to a more generic one, so people can reuse it if they want to hide further elements in the future

Handling of the --hide-ui-dir-config flag and added multi-platform code for opening a folder

Adds icons on the first 3 tabs to directly open the corresponding images output directory

fixed some [send to..] buttons to work properly with all tabs

rework progressbar/preview to work with new gradio
remove unnecessary create style button
added link to alternative colab