Prefix parser tests files with 'proofreadpage_'

The parser test suite use the name of the text file to forge a class
which in test output would show as:

Pagelist::testParserTest.testParserTest with data set #0
Pages::testParserTest.testParserTest with data set #0

Prefix the text files with 'proofreadpage_' to have classes named such
as:

 Proofreadpage_pagelist
 Proofreadpage_pages

That will let us easily find out where the tests come from.

Change-Id: I71c4c9347bb680176af63174cd6315c8127d22f2