Interface works; optimization: predkdsize, supersort, compareyzx, splitcompare started; iteration orders: preorder, inorder started

AbstractTrees print_tree prints not chaotic anymore; rm subtree(string) from node struct; init base.jl, init printing.jl, supersort: rm for loop, rm if else; splitcompare: rename one char variables (a,b,etc.); buildtree: define functions used externally, define valiables/arrays needed to use functions (e.g. temp_array) internally; 2i(+1)->getleft/getright; insertnode: rm checksubtree function, use getindex; isleftchild: changed to determination by index (before: iteration via parent); symdec & deletenode: adapt to no subtree in struct