Build was failing on ofborg on platforms.aarch64 due to
missing muparserx library built for aarch64. Added notes about
this issue & when build could be expanded.
Qiskit Aer - High performance simulators for Qiskit.
This commit follows the new Qiskit scheme of breaking one large package
into smaller packages (terra, aer, etc), and then having a single
meta-package "qiskit" that comprises them.