refactor page-leave-warning on unsaved edits

* removed usage of prototype
* extracted code into separate file
remove usage of link_to_remote_if_authorized
remove usage of prototype in toggle_link
refactor _tabs.html.erb to meet our coding guide
remove prototype usage in tab js logic

also extract the tab handling into a separate file,
which is included in application.js.erb
WIP - adding padding span to last visible row.

currently not working with level setting.
save current tab state in browser history
removed prototype usage of observeProjectModules()
Level expansion now keeps track of last visible row.
Refactored code into timelines helper.
Added a test class for timeline table helper.
refactored hideOnLoad
Changelog: Mark API v2 as deprecated
Merge pull request #1227 from opf/feature/refactor_page_leave_warning

[prototype->jQuery] Refactor page-leave-warning on unsaved edits
Merge pull request #1228 from opf/fix/remove_usage_of_link_to_remote_if_authorized

[prototype->jQuery] Remove usage of link_to_remote_if_authorized
Merge pull request #1230 from opf/fix/remove_usage_of_prototype_tab_js_logic

[prototype->jQuery] Remove usage of prototype tab js logic
Merge pull request #1229 from opf/fix/remove_usage_of_prototype_in_toggle_link

[prototype->jQuery] Remove usage of prototype in toggle_link
Merge pull request #1233 from opf/fix/remove_prototype_from_parts_of_project_create_form

[prototype->jQuery] Removed prototype usage of observeProjectModules()
Merge pull request #1236 from opf/fix/prototypify_hol

[prototype->jQuery]  Refactored hideOnLoad
Merge pull request #1235 from opf/fix/timelines-space-at-bottome-7249

Fix/timelines space at bottome 7249