Added functionality to change number of types between runs (untested)
Added python interface for adding and listing types
Added C++ unit test in test_pdata for adding types
Added python unit tests

and fixed type-related error message in external.periodic()
Fixed problem when types are changed in BDNVT(Rigid) simulation
Make initialization from snapshots with different numbers of types work

also remove two annoying notice(4) messages
Add one more unit test for pair.table
Sanity check for adding duplicate types
Merged in change_num_types (pull request #5)

Allow changing the number of particle types

fixes #19
Fix bdnvt_rigid

per-type parameters would be overwritten when
number of types change
Merged in bdnvt_rigid_fix (pull request #7)

Fix bdnvt_rigid
make error of adding existing types a warning
add line break
Output type name
Merged in add_type_warning (pull request #9)

Make adding already existing types a warning
Fix a small typo.

An assert wasn't checking the 3rd tag in harmonic angle force compute.