Bug 796819 - bad icon with Spanish localization

Drop translations of the 'gnucash-icon' string from our po files
and add a note for translators to not translate this string or
use the litteral 'gnucash-icon' as translation

gnucash/gnome/gnucash.desktop.in.in

@@ -6,6 +6,7 @@ Name=GnuCash
 GenericName=Finance Management
 Comment=Manage your finances, accounts, and investments
 Exec=gnucash %f
+# Icon file name, do not translate or use "gnucash-icon" as msgstr
 Icon=gnucash-icon
 StartupNotify=true
 Terminal=false

po/es.po

@@ -5168,7 +5168,7 @@ msgstr "Gestión Financiera"
 
 #: gnucash/gnome/gnucash.desktop.in.in:10
 msgid "gnucash-icon"
-msgstr "ícono-gnucash"
+msgstr ""
 
 #. Translators: The abbreviation for 'Reconciled'
 #. in the header row of the register. Please only

po/nl.po

@@ -5164,7 +5164,7 @@ msgstr "Financieel management"
 
 #: gnucash/gnome/gnucash.desktop.in.in:10
 msgid "gnucash-icon"
-msgstr "gnucash-icoon"
+msgstr ""
 
 #. Translators: The abbreviation for 'Reconciled'
 #. in the header row of the register. Please only