Cleanup the .desktop file

[nemo] Rename icon from "FingerTerm" to generic "Terminal"
[nemo] Fix single-instance by removing explicit invoker usage
[nemo] Remove unnecessary key/value pairs in .desktop file

fingerterm.desktop.nemo

@@ -1,10 +1,5 @@
 [Desktop Entry]
-Encoding=UTF-8
-Version=1.0
-Name=FingerTerm
-GenericName=FingerTerm
-Comment=Terminal emulator
-Exec=/usr/bin/invoker --single-instance --type=e /usr/bin/fingerterm
-Terminal=false
 Type=Application
+Name=Terminal
+Exec=fingerterm
 Icon=icon-l-terminal