Deterministic sort order of index entries

The current impl. sorts index file lines only by project name. But this leaves random the ordering between various systems of the same project.

The proposed change sorts index elements as text lines, thus all elements are taken into account.

Example. In this dist: http://alpha.quicklisp.org/dist/qlalpha/2014-07-07/systems.txt

```
buildnode buildnode buildnode alexandria cl-interpol cl-ppcre closure-html collectors cxml flexi-streams iterate split-sequence swank symbol-munger
buildnode buildnode-excel buildnode-excel buildnode
buildnode buildnode-html5 buildnode-html5 buildnode
buildnode buildnode-kml buildnode-kml buildnode
buildnode buildnode buildnode-test buildnode buildnode-xhtml lisp-unit2
```
As you see, the last like is out of order