Add token create subcommand for identity v3 api

Implements token create subcommand which is an equivalent of keystone
token-get command. Original "wrap" parameter for keystone token-get is
not implemented yet due to cliff Bug #1269299

This is a part of: blueprint add-identity-token-support

Change-Id: I2255021c9d1f10f757686583b1ebe40b5f3a9ecb
Merge "Add token create subcommand for identity v3 api"