Allows disabling of timestamps when importing posts

fixes #1696

- this is a temp workaround until full fledged support
is added directly to bookshelfjs
- when importing we use the import json blob’s timestamps
as the value that’s set in the DB 
- added tests for this change
Path, url and subdir cleanup & test

issue #1754

- remove path (it was only used once, and not needed)
- change webroot to subdir
- add unit tests for config.paths
- various other cleanup
- renamed client-side ghostRoot to subdir
- added url helper for client
Merge pull request #1764 from ErisDS/path-cleanup

Path, url and subdir cleanup & test
Static pages do not use dated permalinks

closes #1753
- Pages are registered to '/:slug/' route if posts are using dated permalinks
Correct ARIA role for pagination helper

Fixes https://github.com/TryGhost/Casper/issues/63
Shared folder asset handling

fixes #1659, fixes #1668

- removed relative asset url from css
- added asset helper to client
- updated references to shared assets
- added functional tests
Merge pull request #1772 from markberger/1753-static-page-url

Static pages do not use dated permalinks
Merge pull request #1769 from ErisDS/shared-assets

Shared folder asset handling
Merge pull request #1759 from hswolff/fix-import-updated-at

Allows disabling of timestamps when importing posts
Fix live theme switching not working on subdirectories

Closes #1770
- Previously, the middleware would check that the route on the stack was an empty string, which worked when there was no subdirectories
- When subdirectories were added, the proper route was only set when
  updating the theme
- Because it was only set when updating, this explains themes working on
  initial load, since the stack location was looking for an empty
  string, which is what the middleware was initialized with
- However, once a new theme was set, it was still look for an empty
  string, which would never exist, which caused the issue
- Now, the route is properly set on initialization of the middleware,
  and then the `config.paths().subdir` property is used for the check
Update import tool to be safe

closes #1681

- import doesn't override user credentials
- import doesn't override theme
- import doesn't kill session
- import does refresh the settings cache
- updated tests, they now use a fixture instead of a generated export
- tests check to ensure import is safe
Merge pull request #1780 from ErisDS/issue-1681

Update import tool to be safe
Merge pull request #1784 from remixz/theme-switching-subdirs

Fix live theme switching not working on subdirectories
Fixing notifications on ugly debug page

- also fixes an issue where the debug tools didn't redirect properly when Ghost was operating in a subdirectory.