Add support for creation of user groups using right panel
of new user group settings overlay being developed as part
of https://github.com/zulip/zulip/issues/19526.
In further commits we will add support for editing user
groups using right panel of the overlay.
This commit also introduces a minor bug related hashchange
for #groups which would be a quick fix once we have UI
for group edit on #groups overlay.
Purushottam Tiwari