Moved file-io load save and loadHttp to bkUtils from plugins
Moved filesys file chooser strategy into bkCore from plugins
Added 'getHomeDirectory' method
Refactored file open related code so format and location type is handled
Merge remote-tracking branch 'origin/master' into dev-refact-file-open
Refactored notebook open and save
Merged from master
Fixed file loading bug by reversing angular's behavior of  auto detecting and parsing JSON responses
Minor fixed code styling
Moved bkApp methods that shouldn't be exposed through app.impl
Got rid of bkCloseSessionApp and other refactoring about file saving
Made angular version back to 1.2.6
Fixed a bug about closing notebook
Merge pull request #139 from twosigma/dev-refact-file-open

Dev refact file open
Removed unused directive bkNotebookEvaluatorsAddEvaluatorPanel
First step to separate evaluatorManager in to eval plugin manager and evaluator manager
Made bkNotebookEvaluators(plugin manager) back to work
Merge remote-tracking branch 'origin/master' into dev-refact-evaluator-managers
Use plugin names instead of urls in tutorial notebooks
Completely got rid of the old evaluatorManager