[gimp] plug-ins: rename "Preset" to "Source type" in WebP export dialog.

[Jehan Pagès <jehanp src gnome org>]

commit 4c1cb9a84ba2c90d9b9a26f4cad580067fc22520
Author: Jehan <jehan girinstud io>
Date:   Tue Nov 15 00:49:43 2016 +0100

    plug-ins: rename "Preset" to "Source type" in WebP export dialog.
    
    The "Preset" feature changes encoding parameters not exposed in our GUI.
    Thus it looks like the option is broken as whatever you select, nothing
    is updated in the export dialog.
    This is also inconsistent with what we call presets in the rest of GIMP:
    they are used to save and load values for all fields as a dynamic and
    editable list (whereas here that's a pre-defined list in libwebp setting
    only a subset of options).
    
    `cwebp` manual defines "preset" as: "Specify a set of pre-defined
    parameters to suit a particular type of source material."
    
    Thus call the field "Source type" and add a tooltip "WebP encoder preset"
    so that people don't expect a way to save settings whereas the ones used
    to the WebP encoder parameters still find their way.

 plug-ins/file-webp/file-webp-dialog.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/plug-ins/file-webp/file-webp-dialog.c b/plug-ins/file-webp/file-webp-dialog.c
index edda3e0..dbb94e9 100644
--- a/plug-ins/file-webp/file-webp-dialog.c
+++ b/plug-ins/file-webp/file-webp-dialog.c
@@ -135,7 +135,10 @@ save_dialog (WebPSaveParams *params,
                     &params->alpha_quality);
 
   /* Create the label for the selecting a preset */
-  preset_label = gtk_label_new (_("Preset:"));
+  preset_label = gtk_label_new (_("Source type:"));
+  gimp_help_set_help_data (preset_label,
+                           _("WebP encoder \"preset\""),
+                           NULL);
   gtk_label_set_xalign (GTK_LABEL (preset_label), 0.0);
   gtk_table_attach (GTK_TABLE (table), preset_label,
                     0, 1, 2, 3,