make installer also look for FIRST_INSTALL.txt file
One of the most common pitfals new users have while trying to install TYPO3 on windows is that they create FIRST_INSTALL.txt file instead of just FIRST_INSTALL.
It is caused by the fact that Windows hides file extensions by default (so users think they create FIRST_INSTALL file, but in fact it was with .txt extension).
I think it would be a good idea to either
- make the install tool also check for file with the txt extension
- or ask user to create FIRST_INSTALL.txt file from the beginning