A directory-category for terminal emulators

This is a mostly cosmetical commit, in the sense it doesn't change the contents
of any package, but reorganizes the overall Nixpkgs expressions.

Terminal emulators are an ubiquitous tool for any Unix user; even the beginners
are routinely familiarized to it. And, manifestly, there are many
implementations of terminal emulators out there, from those traditionally made
in C and C++ to those written in Haskell and Go.

Terminal emulators deserve more highlight. This commit does that by creating a
category for them.

pkgs/applications/terminal-emulators/xtermcontrol/default.nix

@@ -0,0 +1,25 @@
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  version = "3.7";
+  pname = "xtermcontrol";
+
+  src = fetchurl {
+    url = "https://thrysoee.dk/xtermcontrol/xtermcontrol-${version}.tar.gz";
+    sha256 = "04m12ddaps5sdbqvkwkp6lh81i8vh5ya5gzcxkrkilsga3m6qff2";
+  };
+
+  meta = {
+    description = "Enables dynamic control of xterm properties";
+    longDescription = ''
+      Enables dynamic control of xterm properties.
+      It makes it easy to change colors, title, font and geometry of a running xterm, as well as to report the current settings of these properties.
+      Window manipulations de-/iconify, raise/lower, maximize/restore and reset are also supported.
+      To complete the feature set; xtermcontrol lets advanced users issue any xterm control sequence of their choosing.
+    '';
+    homepage = "http://thrysoee.dk/xtermcontrol";
+    license = stdenv.lib.licenses.gpl2;
+    platforms = stdenv.lib.platforms.unix;
+    maintainers = [ stdenv.lib.maintainers.derchris ];
+  };
+}