Allow workflows to support multipart POST.

Enabled by setting multipart = True in the Workflow sublcass.

Required for blueprint: heat-ui

Change-Id: I557c7ad99333d69241e7fa7726f1db30939c8d2c
register replace_underscores filter for templates

Required for blueprint: heat-ui

Change-Id: I0c5dbb82254f59f375fa82d64567a94e8fe9dac8
Merge "Allow workflows to support multipart POST."
Merge "register replace_underscores filter for templates"