This big patch, fix xhtml code, and user interface.
It Delete the term of budget period and use it as "Root Budget".
It add improvment on UI, adding tooltip, and table tree.
* there can be more than 1 active period. This has been added to deal with temporary budgets (like "10000€ to spent in the next 3 months")
* all active budgets are retrieved
* budget available for everyone now displayed correctly
also :
* fixing some hardcoded values
* removing a warn
* budget period management
* budget management (budgets lines are defined for a given budget period)
budget_owner_search is the popup to select a librarian as budget owner
