Note: Requesting Meta Attribute

Added metaPostID and metaSiteID helpers to Note model class.
Notifications: Minor style updates
Notifications: Minor style updates. Part 2
Notifications: Minor style updates. Part 3
Automattcher Notes: Pushing native reader on tap
Adds a header label to WPContentView.

If a the comment detail view is using a note content provider, add a header to the top that provides some context about the comment being viewed.

Fixes #1444.
Fixing frame property access.
Merge remote-tracking branch 'origin/develop' into issue/1507-matcher-notifications

Conflicts:
	WordPress/Classes/Note.h
	WordPress/Classes/Note.m
Use horizontal padding constant to match up with the other views.
Merge remote-tracking branch 'origin/develop' into issue/1507-matcher-notifications

Conflicts:
	WordPress/Classes/NotificationsViewController.m
Merge branch 'develop' into issue/1444-comment-context
Use existing controller methods to load web view, so they will provide credentials for private sites.
Set header label frame's autoresizingMask to fix overflow on iPad.
Moved header label to CommentView subclass.
Removing an extra line break.
Merge remote-tracking branch 'origin/develop' into issue/1507-matcher-notifications

Conflicts:
	WordPress/Classes/NotificationsViewController.m
Merge pull request #1523 from wordpress-mobile/issue/1507-matcher-notifications

Issue #1507: Fixes Automattcher Notes DetailView
Use a constant for the label's vertical inset size.
Merge pull request #1526 from wordpress-mobile/issue/1444-comment-context

Adds a header label to CommentView.
Merge branch 'develop' into issue/1538-cleanup-mixpanel

Conflicts:
	WordPress/Classes/NotificationsViewController.m