Supports bash_completion for heatclient

bash_completion feature can improve CLI user experience, projects like
nova, keystone, and cinder already support it.

NOTE: this patch just provides simple functionality, which means cache
for IDs and names is not used (like nova).

Closes-Bug: #1260939
Change-Id: I327e884e1c5907c9ff6f31131c70aee659cca58e