overhaul prompt management; make it easier to add/remove things to {,r}prompt over time

modules/base_prompt.zsh

@@ -0,0 +1,19 @@
+#    PROMPT="%{$fg_bold[cyan]%}%n%{$fg_bold[white]%}@%{$fg_bold[magenta]%}%m %{$fg_bold[white]%}%~ %# %{$reset_color%}"
+#    RPROMPT="%(?..%{$fg[red]%}%? )$RPROMPT"
+
+function prompt_userathost () {
+    print "%{$fg_bold[cyan]%}%n%{$fg_bold[white]%}@%{$fg_bold[magenta]%}%m %{$fg_bold[white]%}%~"
+}
+
+prompt_functions+=prompt_userathost
+
+function rprompt_clock () {
+    print "%{$fg_bold[black]%}%T"
+}
+
+function rprompt_retval () {
+    print "%(?..%{$fg[red]%}%?)"
+}
+
+rprompt_functions+=rprompt_clock
+rprompt_functions+=rprompt_retval