Release Name: 5.2

Change Log
The following bugs were fixed in OpenMM 5.2:

1870: IntArray methods missing from OpenMMFortranWrapper.cpp
1871: CustomIntegrator fails to compute kinetic energy when system has
massless particles
1881: Using GB with a cutoff should disable reaction field
1883: Errors in CustomIntegrator when multiple steps use random numbers
1885: addHydrogens() fails for ACE and NME
1902: Deserialized force produces swig error when added to a system