refactoring api::v2::pe_controller.
Refactored PlanningComparisonService to make it more readable.
comparisons for: status, type, responsible.

contains some bugfixes too.
changelog.
make every attribute comparable.

for now: add project.
tests for time comparisons.
Merge remote-tracking branch 'origin/feature/rails3' into feature/magic_comparison

Conflicts:
	app/assets/javascripts/timelines.js
	app/views/timelines/_timeline.html.erb
	doc/CHANGELOG.md
changelog added. sorted.
added detail-views and journals for planning-elements
make sure, that you use the userfriendly attribute only in the user_friendly block
removed some notes
fixed the journalizing-specs

some extensive stubbing of the journal was needed to test that the api
reports the correct values.
Merge branch 'feature/rails3' into feature/migrate_api_views_to_rabl
Merge remote-tracking branch 'origin/feature/rails3' into feature/magic_comparison
removed redundant status, project and type-elements from the index-view
bugfix. rename some due dates.
get timeline rows and cells. test status.
re-added the planning-element detail-view
removed an unnecessary intermediate element from the journals, added a rake task to create some fake projects
Removed a redundant change-element from the journals-xml