WebSearch: handles "find feb 12"

* Converts SPIRES syntax "find feb 12" to "year:2012-02".
  (closes #948)

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
WebSearch: tweaks SPIRES two-digit search

* Instead of having a window ending at the current year
  e.g. for 2012: 1913 -> 2012
  the new two-digit year window is 10 years ahead:
  e.g. for 2012: 1923 -> 2022
  This permits to search for near future dates.

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>