conda improvements

[daler]

• add ca and conda_deactivate_all functions, and run conda_deactivate_all when starting a new tmux session or pane
• add documentation for this new conda setup
• improved start_agent to use Mac login
• new command --mac-stuff for post-installation Mac
• new command --install-tmux command esp useful for Mac
• use Mambaforge when installing conda; change --install-miniconda to --install-conda; this support Mac ARM64 architecture
• when running --set-up-vim-plugins, run :PlugInstall automatically unless MANUAL_PLUG_INSTALL=1
• add recommended order of operations in setup.sh