CKAN server selection dialog

[wilhelmberg]

improve display of ckan instances

[wip] CKAN Instances Dialog

select server from list and load data

[wip] custom servers

limit intances list to those with an API URL

[wip] CKAN servers from ckan.org instances

add/remove custom servers

misc:

• overhaul settings dialog
• fix filename discovery

fix type in plugins.xml

point plugins.xml to dev branch

update zip

fix explorer not opening the right directory on Windows

v0.4 RC1

Fixes #

Proposed changes and what do they do: