Fix many package descriptions

(My OCD kicked in today...)

Remove repeated package names, capitalize first word, remove trailing
periods and move overlong descriptions to longDescription.

I also simplified some descriptions as well, when they were particularly
long or technical, often based on Arch Linux' package descriptions.

I've tried to stay away from generated expressions (and I think I
succeeded).

Some specifics worth mentioning:
 * cron, has "Vixie Cron" in its description. The "Vixie" part is not
   mentioned anywhere else. I kept it in a parenthesis at the end of the
   description.

 * ctags description started with "Exuberant Ctags ...", and the
   "exuberant" part is not mentioned elsewhere. Kept it in a parenthesis
   at the end of description.

 * nix has the description "The Nix Deployment System". Since that
   doesn't really say much what it is/does (especially after removing
   the package name!), I changed that to "Powerful package manager that
   makes package management reliable and reproducible" (borrowed from
   nixos.org).

 * Tons of "GNU Foo, Foo is a [the important bits]" descriptions
   is changed to just [the important bits]. If the package name doesn't
   contain GNU I don't think it's needed to say it in the description
   either.

1 files changed, 1 insertions, 1 deletions

diff --git a/pkgs/tools/compression/rzip/default.nix b/pkgs/tools/compression/rzip/default.nix
index ca8d356abb3e..4460ae6edf3e 100644
--- a/pkgs/tools/compression/rzip/default.nix
+++ b/pkgs/tools/compression/rzip/default.nix
@@ -10,7 +10,7 @@ stdenv.mkDerivation {
 
   meta = {
     homepage = http://rzip.samba.org/;
-    description = "The RZIP compression program";
+    description = "Compression program";
     license = stdenv.lib.licenses.gpl2Plus;
   };
 }