Mostly changes to prep for sort by column (name, size, or date) feature.

Moved 'Select All [x]' from Index_Page() to Table_of_Files(), to table header.
Associated style changes for #mcd_submit
hte(): now returns raw input if htmlspecialenities returns null.
New Language keys:
  $_['MCD_margin_R'] = '1.0em'; //For [Move] [Copy] [Delete] buttons
  $_['Name'] = 'Name';
  $_['Size'] = 'Size';
  $_['Date'] = 'Date';
  $_['Source'] = 'Source';  (added in 3.4.21)
In ES langauge file: $_['Clear_All'] = 'Limpiar Todos';
New js function: format_number(number)  : 1234567 to 1,234,567