Forest update from Mefisto part 1

Add new palms, savanna

Update existing palms

Add jungle images

Updates to existing tropical forest + new rainforest waiting for
comments from Mefisto

changelog

@@ -39,6 +39,8 @@ Version 1.11.0+svn:
    * Handle an exception in the SDL_net-based network code (bug #20205)
  * Terrains:
    * Added Unwalkable Overlay terrain (^Qov)
+   * Added Dense Palm (^Ftp), Savanna (^Fts) forest terrains
+   * Updated existing desert palms (^Ftd)
  * User interface:
    * Healing animations are now played when poison is cured.
    * Moving units to a selected hex field