v2.0.0-beta.0

Increment to v2.0.0-alpha:

New features:

• Atom type embedding
• Model deviation for virial

Enhancement:

• Improved documentation
• Better support for dipole and polarizability learning
• bit operations to encode neighbor information
• MPI support for atomic model deviation #628
• UT for GPU code #569
• UT for model compression #586
• Test Lammps build #600

Bug fixings

• cuda memory access error #566
• relative force model deviation is not copied back at single precision #599
• correct way of allocating memory in float precision #612
• fix TB logdir remove bug #617
• Append out_file when lammps restarts #640