I can show important informations to my team

- The cardwall will provide a "Card semantic" (as agile dashboard does for initial effort)
- The card will be configurable per tracker in the very same way it's done for tool tip as of today (fields are displayed one after another in column)
- Today's hardcoded fields (remaining_effort, assigned to, title, impediment) are displayed by default
- Card edition is hard coded as of today (only remaining_effort and assigned_to, same behaviour as today). No way to edit other fields inline yet (might be possible later but it's another story).
- Once configured, there is no mandatory fields on card (might end up to an empty card).
- By default there still the "edit / add" menu on top right
- All things represented as cards are concerned (ie. "tasks/bugs/..." and stories in cardwall and whatever is displayed when using the cardwall renderer in tracker)

Technically:
- This include a refactoring of the way cards are built to reduce the performance impact of per card field selection.

Manuel made a spike that remove the callback/mapper:
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WIP: Try to reduce the workload of building cardwall

This is a preliminary work to streamline as much as possible the building
of the cardwall.
Ideally we should tend to:
-> identifying the data we need
-> fetching the data, only what should be display, but all at once
(as much as possible)
-> building the board with cards and cell (presenters)

Change-Id: I743e5c0ed537450a877a48d6a6f41fbff2290da2
https://tuleap.net/plugins/git/index.php/101/view/61/?p=u%2Fvaceletm%2Ftuleap%2Fdev.git&a=commit&h=5d61afa2e6415349814a6fb3a0de19dc4fb62dd1
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However, due to some caching hell, this commit actually increase the number of sql queries (470 -> 500 on my test data).
So, there is mabye something to pick-up but definitively not merging as is