patch by Cjkjvfnby cleaning up ES stringtable, but not substantively updating its actual translations
 * Removed keys that are not used as of r 7788
 * Removed keys that were themselves wrongly translated  ([[<key>]] is reference and should not be translated)
 * Formated empty line and comments exactly the same as in en.txt.

git-svn-id: svn://svn.code.sf.net/p/freeorion/code/trunk@7798 dbd5520b-6a0a-0410-a553-f54834df5b05