Fix selection of spaces in spaces/index

jQuery's `$().on("hover")` is now `$().hover()`.
Fix error in Space model added by 2a21260b4411

The space needs tags, they are used for the attachments.
Remove lots of vendored assets that are not used anymore

Most of them are not referenced anywhere in the code anymore.
A few of them are still referenced in old files. But if they are needed
in the future we will have to find better alternatives or at least
update their versions (most of them were more than 2 years old).
Fix loading resources in some controllers after cc9d1179bfc

Explicitly set that spaces have to be found by 'permalink'.
Several small layout improvements

Fix useless x-scrollbar in modals.
Trying to use a standard layout for buttons and content blocks.
ome changes in buttons in sidebars and content blocks in user's home.