Add toggle for showing OK in non verbose status

Adds the toggle POWERLEVEL9K_STATUS_OK_IN_NON_VERBOSE for more
customizability. If POWERLEVEL9K_STATUS_VERBOSE is false and
POWERLEVEL9K_STATUS_OK_IN_NON_VERBOSE is true, the status prompt will
show the OK visual identifier like in verbose mode. The prompt will show
the OK identifier even if POWERLEVEL9K_STATUS_OK_IN_NON_VERBOSE is false
in verbose mode.

powerlevel9k.zsh-theme

@@ -739,6 +739,7 @@ prompt_rvm() {
 
 # Status: return code if verbose, otherwise just an icon if an error occurred
 set_default POWERLEVEL9K_STATUS_VERBOSE true
+set_default POWERLEVEL9K_STATUS_OK_IN_NON_VERBOSE false
 prompt_status() {
   if [[ "$RETVAL" -ne 0 ]]; then
     if [[ "$POWERLEVEL9K_STATUS_VERBOSE" == true ]]; then
@@ -746,7 +747,7 @@ prompt_status() {
     else
       "$1_prompt_segment" "$0_ERROR" "$2" "$DEFAULT_COLOR" "red" "" 'FAIL_ICON'
     fi
-  else
+  elif [[ "$POWERLEVEL9K_STATUS_VERBOSE" == true || "$POWERLEVEL9K_STATUS_OK_IN_NON_VERBOSE" == true ]]; then
     "$1_prompt_segment" "$0_OK" "$2" "$DEFAULT_COLOR" "046" "" 'OK_ICON'
   fi
 }