Add create plan page
add tree structure plan_item(session) ->  day -> exercise
add up/down/delete actions for plan_item, session counts
directive for table-selects
add arrows and delete action for days
Add drag & drop for exercises
add dummy for server logic
add build_from method to PlanItem
write specs for plans_controller
add destroy_plan_session callback + specs
Merge pull request #19 from Minisai/R-13_Create_plan_page

R-13: Create plan page