Removed bookmarking talk + fixed orientation

 * Editorial cleanup
 * Rewrote orientation to match latest spec (closes #150)
 * Removed "bookmarking" from spec (closes #164)
Merge pull request #166 from w3c/orientation_fixes

Removed bookmarking talk + fixed orientation
First stab at CSP policy tightening:

* Factor out "Associating a resource with a manifest"
* Note HTTP caching and custom caches in "Fetching a manifest"
  and add an example how HTTP cache directives could be used
* Augment "Processing the manifest" with steps to append
  Content-Security-Policy header
* Add "csp member" section

Needs review.
Address Marcos' review comments.
Merge pull request #162 from anssiko/csp

First stab at CSP policy tightening
Rename 'default_orientation' to 'orientation'.
Merge pull request #170 from mounirlamouri/device_orientation_bikeshed

Rename 'default_orientation' to 'orientation'.
Update 5.8 to consider display modes as a string instead of an Array of strings.
Update the orientation section to match the Screen Orientation spec.
Merge pull request #171 from mounirlamouri/orientation_update

Update the orientation section to match the Screen Orientation spec.
update example to have display be a string
Update 'display modes' to include fallback chain.
Fix display mode processing algorith.
Update the algorithm processing the manifest.
Define fallback mode and make 'browser' explicitely mandatory to implement.
tidy run
Merge pull request #173 from mounirlamouri/display_chain

Change 'display' to be a string and have a fallback chain
Fix example to use manifest.json
Merge pull request #174 from mounirlamouri/example

Fix example to use manifest.json
Clarify goals, add pointers to v2 issues.