Test compatibility with Drude trajectories

[drroe]

Make certain that cpptraj correctly identifies Drude particles.

[drroe]

Drude particles should be recognized as a separate element.

[drroe]

molinfo short has weird info for the test PSF:

#Mol  Natom  Nres  Res0  Res1 Name C   
    1   372     2     1     2 SER  PROA     2     3     4 THR  PROA     5     5     9 GLU  PROA     2    10    11 THR  PROA     1    12    12 LYS  PROA
    2     1     1     2     2 TRP  PROA
    3     1     1     4     4 TRP  PROA
    4     1     1     9     9 TRP  PROA
    5     1     1    11    11 TRP  PROA
    6     2     1    13    13 POT  IONS
    7     2     1    14    14 POT  IONS
    8     2     1    15    15 POT  IONS
    9     2     1    16    16 POT  IONS
   10     2     1    17    17 POT  IONS

[drroe]

> molinfo short *
  [molinfo short *]
#Mol Count Natom  Nres
SER      1   372    12
TRP      4     1     1
POT      5     2     1
CLA      7     2     1
SWM4  2041     5     1

[drroe]

Should be addressed by #1099, #1100