- added a new defs var, TBROBOCOPSEMAIL

  * tbsetup/power_mail.pm.in:
    - add some new info to robot powerup mails

  * db/libdb.pm.in:
    - add a new function to determine if an experiment contains nodes of a
      given class/type

  * tbsetup/swapexp.in:
    - check if exp is a robot exp; that is, if it has robots or motes; if
      so, cc error msgs to TBROBOCOPSEMAIL in addition to TBOPS