Vim config comments & more

[daler]

• [vim] cleans up vim config to be more streamlined, deferring to online docs for documentation
• [vim] always enter insert mode when switching to nvim terminal
• [vim] use zenburn plugin (plus termguicolors) for nicer colorscheme
• [bash] fixes an issue where the new conda_deactivate_all would get stuck in the while-loop
• [bash] no need to run ca first on every bash running in tmux
• [bash] check for conda first before running conda_deactivate_all
• [bash] added new hostlist bash function to .functions
• [install] when first installing plugins, don't automatically quit vim/nvim so you can confirm everything worked
• [docs] docs review and update (including updated changelog)
• [test] improve docker test