Added subroutine file_read_end_error() to system.f90

* Added subroutine file_read_end_error() to system.f90:
  * Prints a message to StdErr on read error or reaching the end of a file while reading,
    and optionally stops the code
Added function timestamp() and subroutine printprogressbar()

* Added function timestamp() and subroutine printprogressbar():
  * timestamp(): returns a Unix timestamp
  * printProgressBar():  prints a text progress bar and Est.time left to screen
Changed currentdatestr

* Changed currentdatestr:
  * currentdatestr: DD/MM/YYYY -> YYYY-MM-DD - unambiguous
  * new variables:
    * currentdatestren: MM/DD/YYYY (US system)
    * currentdatestrnl: DD/MM/YYYY (Dutch/EU system)
  * renamed old currentdatestren, currentdatestrnl -> currentdatestrenl, currentdatestrnll
    * extra l: long - contains DoW name and full month
printProgressBar(): Make timestamp0 an optinal argument

* printProgressBar(): Make timestamp0 an optinal argument:
  * if present, print estimated remaining time