Modal fixes - 2 columns, padding, header, membership

Adds padding to tab-content which takes care of proper
spacing between tabs and tab-content.
refactors tabs styling - match modal and non-modal tabs
Changes modal header h3 margin to save space.
Cleans up Membership widget styling
Unifies 2 column layout in modals using bootstrap columns
Changes create and update image modal template as an example.
The rest of the views is changed in subsequent patch

Closes-Bug: #1354505
Change-Id: Idca2a2dbdea8cdacc37061faa52004b1020b1bf0
Merge "Modal fixes - 2 columns, padding, header, membership"
Improving more projects link in context selection

The existing icon is a cog which implies making a settings change.
Changing to a list icon to match more closely what is achieved by
the link.

Also, adding the icon to the link rather than having it separate,
this is more consistent with the rest of the UI.

Closes-Bug: #1398515
Change-Id: I10c998c939d47b0a8ef6bbd13c66bddcba12b14b
Merge "Improving more projects link in context selection"
Merge branch 'master' of https://github.com/openstack/horizon