Make cursor styling more robust; disable it on Konsole

Minimally fixes #6, by disabling cursor styling on Konsole. A complete
fix needs to use the Konsole-specific codes, possibly versioned to take
the upcoming fix (in 18.08?) for Konsole [bug 347323][1].

This change also avoids printing the cursor-styling sequences at all if
no cursor style is defined. Previously, the default style was set
regardless. This will ensure that any similar problems with other
terminals will only show up if the user requests cursor styling
explicitly.

1: https://bugs.kde.org/show_bug.cgi?id=347323

zsh-vim-mode.plugin.zsh

@@ -532,35 +532,31 @@ vim-mode-set-cursor-style() {
        || -n $MODE_CURSOR_SEARCH ]]
     then
         case $keymap in
-            vicmd)        set-terminal-cursor-style ${=MODE_CURSOR_VICMD} ;;
+            DEFAULT)      set-terminal-cursor-style ;;
+            vicmd|visual|vline)
+                          set-terminal-cursor-style ${=MODE_CURSOR_VICMD} ;;
             isearch)      set-terminal-cursor-style ${=MODE_CURSOR_SEARCH} ;;
             main|viins|*) set-terminal-cursor-style ${=MODE_CURSOR_VIINS} ;;
         esac
     fi
 }
 
 vim-mode-cursor-init-hook() {
-    vim-mode-set-cursor-style ''
+    vim-mode-set-cursor-style viins
 }
 
 vim-mode-cursor-finish-hook() {
-    set-terminal-cursor-style
+    vim-mode-set-cursor-style DEFAULT
 }
 
-case $TERM in
-    # TODO Query terminal capabilities with escape sequences
-    # TODO Support linux, iTerm2, and others?
-    #   http://vim.wikia.com/wiki/Change_cursor_shape_in_different_modes
-
-    dumb | linux | eterm-color )
-        ;;
+if [[ $TERM = (dumb|linux|eterm-color) ]] || (( $+KONSOLE_PROFILE_NAME )); then
+    :
+else
+    vim_mode_keymap_funcs+=vim-mode-set-cursor-style
 
-    * )
-        vim_mode_keymap_funcs+=vim-mode-set-cursor-style
-        add-zsh-hook        precmd         vim-mode-cursor-init-hook
-        add-zle-hook-widget line-finish    vim-mode-cursor-finish-hook
-        ;;
-esac
+    add-zsh-hook        precmd      vim-mode-cursor-init-hook
+    add-zle-hook-widget line-finish vim-mode-cursor-finish-hook
+fi
 
 # Restore shell option 'aliases'. This must be the last thing here.
 if [[ $_vim_mode_shopt_aliases = 1 ]]; then