[i18n]> Pot update using WordPress tools make.pot

Several fixes
1) welcome.php page ready for i18n again.
It adds 40 strings, not sure it might bring some speed issue.
And it will make francophone users happy again when i'll push the french.po ;)

2) [i18n]> Pot update using WordPress tools make.pot
props to @samikeijonen

3) Remove strings.php cause the new tool to create the pot doesn't need it anymore

Note: if you really want to improve the language folder, then you should remove all the .po files, leave only the .mo files and create a simple howto.text file to explain how to use a pot file ;) 

If you want i got one already ready ;)
See ya