Updated description of create volume type dialog

The existing description is not very helpful, it does not metion
the extra specs that users need to deal with in order to make the
volume type usable.

Updated the description to guide users to set up the extra specs
in Horizon UI.

Closes-Bug: #1325726

Change-Id: I68db21cb45e6fa787ae4845aa8690ab6185dbed8
Some 'Create' buttons missing '+' icon

Small bug after https://review.openstack.org/#/c/107042/ was merged.

Image Custom Properties
Volumes Extra Specs
Admin > Projects

Closes-Bug: #1349606
Change-Id: I023b10be4f409d311c30f616b2bf24432af9551c
Merge "Updated description of create volume type dialog"
Imported Translations from Transifex

Change-Id: I088e3dc6a1e3c74b8e4ccfc4ebc8f7a3b64a8d35
Merge "Some 'Create' buttons missing '+' icon"
Merge "Imported Translations from Transifex"