Make importer more robust for tags

Closes #3242

- Add checks for valid fields in tags and posts
- Add unit test with empty tag export data file
- Add unit test with empty post export data file
Avoids duplicate notification / transition

no ref
- Let application.js handle transition after setup
- Remove duplicate loading of server notifications
Fixing pg build.

refs #2499
- Properly reference pg client
- Fix broken sql queries
Update user roles in store after owner transfer

Closes #3466
- Transferring the owner role is now done via a separate
  endpoint and not through Ember-Data.  As a result the
  user role data needs to be updated manually.
- Updated the owner endpoint to return a response body
  containing the updated user objects.
- Updated tests.
Complete frontend multi-user features

closes #3076

- author RSS pages
- fixes page_url / pagination helper
- add 'author' option to has helper
- tests for author pages, author rss pages and helpers
Merge pull request #3480 from jaswilli/issue-3466

Update user roles in store after owner transfer
Merge pull request #3477 from halfdan/duplicate-notification

Avoids duplicate notification / transition
Cleanup CodeMirror shortcuts.

* Add titleize utility function.
  * Capitalizes first word.
  * Capitalizes all words not contained in simple article/conjunction
    list.
* Enable shortcuts for `uppercase`, `lowercase`, and `titlecase`.
* Fix header shortcuts
  * Ensure that header shortcuts do not duplicate text.
  * Make headers idempotent (pressing `ctrl+alt+1` then
    `ctrl+alt+2` does not make `# # # blah`.
Merge pull request #3476 from rwjblue/moar-shortcuts

Enable uppercase, lowercase, titlecase shortcuts.
Shorter notifications

Basic notifications are unnecessarily verbose and, in some instances, even cause line-wrapping to occur. This change shortens them to short, concsise statements to indicate what action has taken place.
Fix naming of export file during migration

No Issue
- The method that generates a filename for the export during
  a migration returns a promise, not the filename directly,
  so the export file was being named [object Object].
Updating HTML for script placeholders
Merge pull request #3479 from ErisDS/issue-3079

Complete frontend multi-user features
Changing second half of script placeholders
The page refresh when oauth token has expired was broken.
Ember simple-auth action "sessionInvalidationSucceeded" was overriden to display a meaningless message.
Merge pull request #3425 from jgable/fixImporter

Make importer more robust for tags
Merge pull request #3485 from jaswilli/migration

Fix naming of export file during migration
Merge pull request #3478 from halfdan/fix-pgsql

Fixing pg build.
Fix for missing author when switching posts

No Issue
- Fixes the case where the authors dropdown in the
  post settings menu has no author selected after
  switching between posts.
Show posts authored by current user.

The current logic allows showing of all EXCEPT the current users posts
(when the current user is an author).

This fixes that.