resolve drag'n'drop from cluster preview box

disabling popup of the preview box on mouseover. Mouseleave does not
work in junction with drag'n'drop, at least with jquery/backbone.
LL-368, LL-365: fixed duplicate addition of entities to timeline

added a method "contains" for EntitiesHelper/ClusterHelper checking
whether an entity is already contained
LL-446: disabled evernote import button

and rearranged buttons in menu
LL-417: new timeline state is not saved to server

it gets saved as soon as it is changed. if it has not been saved to
server but needs to be retrieved, start and end values of timeline state
are simply null
LL-417: Timeline browses to last bit automatically

if the timeline hasn't got a stored start/end range. UserData now passes
all new user events at once in the data model
LL-417: fetching user events on load of user, not per timeline
integrate schema file into require system
add jquery-ui to require deps and bust cache
subsume evernote bit types under entity type
decision logic for multiple bit types

if a bit has got multiple types this algorithm decides which one to choose
to use as the rendered icon
LL-448: entityDescsGet integrated

UserData now fetches entities belonging to user events via
entityDescsGet, taking this function over from OrgaEntityData and UserEventData.