If the cached html_field for a markdown_field is `nil` while the
mfarkdown_field is not, it needs to be refreshed.

This reflects better that it validates paths instead of a namespace model

Since the namespacevalidator now knows the difference between a
top-level and another path, this could all be handled there.

`Project` uses `ProjectPathValidator` which is now a
`NamespaceValidator` that skips the format validation.

That way we're sure we are using the same collection of reserved
paths.

I updated the path constraints to reflect the changes: We now allow
some values that are only used on a top level namespace as a name for
a nested group/project.

- Upgrade Gitaly-version

Improved todo message when an issue is assigned to yourself.
- The new message when an user assign to himself an issue or a mr is: "You
assigned issue xx to yourself"
- The new message when an user adds a todo to himself is: "You added a
todo for issue xx"
- The new message when and user mention himself is: "You mentioned
yourself on issue xx"
- The new message when an user directly address himself is: "You
directly addressed yourself on issue xx"
- The new message when an user mark himself as an approver is: "You set
yourself as an approver for merge request xx"

- Backup-rake-spec fixed. Storage config broken
- Use rugged to compare branch/tag-count in specs
- upgrade gitaly

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

- We upgraded `rugged` to 0.25.1.1 in !10286 for %9.1

- Prior to this upgrade, the default sort order for commits returned by
  `Gitlab::Git::Repository#find_commits` was `Rugged::SORT_DATE`, which the
  graph relied on.

- While upgrading `rugged`, the MR also changed this default to
  `Rugged::SORT_NONE`, which broke commit ordering in the graph.

- This commit adds an option to `Gitlab::Git::Repository#find_commits` to sort
  by date, and changes the graph builder `Network::Graph` so it explictly
  requests the `:date` sort order

Because the post-processing of the rendered README is dependent on the
context (i.e. the current user), do the post-processing when the
README is being displayed.