[Repository] Repo Explorer

[troussej]

I'd like to add an enhanced version of the repo page, with a new UI, that is not constrained by the original UI of dyn/admin. It could be a separate thing from the existing repo page.

Some goals/features:

• [x] Cross repo calls ( so it could be just a popup, like Dash)
• [x] Ajax based -> experience would be more fluid, instead of reloading the whole page + BDA each call.
• [ ] use a proper model for the objects, don't just rely on the xml, so it's easier to manipulate/extend
• [ ] Existing features : On the fly edition, links to other items, item tree, etc
• [ ] Pop over with item definition (reuse existing xmldef parsing)
• [ ] Help with rql syntax
• [ ] Better UI : close/collapse individual results, sorting. -> here I would transpose the columns/lines, like a sql result.
• [ ] Like in Dash, partial submit of the text (from #57 )