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
Fixing pg build.

refs #2499
- Properly reference pg client
- Fix broken sql queries
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].
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.
Merge pull request #3490 from jaswilli/psm

Fix for missing author when switching posts
Merge pull request #3493 from rwjblue/fix-posts-post-author-list

Show posts authored by current user.
Merge pull request #3487 from JohnONolan/notification-copy

Shorter notifications
Set postgres version to 9.3

refs #2499
Updating Casper to latest
Update importer for MU

closes #3285

- remove apps stuff for now
- if there is a single user, behave the same as before, overriding
  non-critical properties of the single owner user
- if there are multiple users, import them like normal resource
Merge pull request #3488 from manuelmitasch/fix-session-invalidation

The page refresh when oauth token has expired was broken.
Merge pull request #3495 from halfdan/patch-1

Set postgres version to 9.3
Remove unnecessary hard refresh on signout.

Refs #3488
- Hard refresh handled by ember-simple-auth.
Merge pull request #3494 from ErisDS/issue-3285

Update importer for MU