feature(file): display file upload limit on file upload form

Refs #6355
feature(groups): Added featured groups as a tab along with groups, popular, discussions

Slightly changed and combined work of @thuvalpakshi
fix(notification): extract notification summary from $params

Fixes #6885
fix(install): Make installer usable on smartphones
chore(install): Point docs links to learn.elgg.org instead of docs.elgg.org

Refs #6784
fix(file): download adds header Content-Length
fix(file): destroy output buffer before sending file
fix(members): prevent members search with empty query
fix(aalborg_theme): selected page menu does not collapse sub menu

Fixes #6979
Merge pull request #6992 from PerJensen/1.9

fix(aalborg_theme): selected page menu does not collapse sub menu
fix(ui): Corrected bad stretching of non-square, large avatars. Now upscaling by width.

Fixes #5602
fix(core): Added missing options array support for ElggUser methods

Fixes #6994 #6993
Merge pull request #7001 from Srokap/ticket_6994

fix(core): Added missing options array support for ElggUser methods
Merge pull request #6968 from tacid/patch-1

fix(file): download adds header Content-Length
fix(router): Can return 'handler' param in `'route', $identifier` hook again

In 1.8, it was possible to delegate to a different page handler by registering
a callback for the `'route', $identifier` plugin hook that looks like so:

```php
$result['handler'] = 'other';
return $result;
```

Then during 1.9 it was changed to expect the key to be 'identifier':

```php
$result['identifier'] = 'other';
return $result;
```

This change makes it so that both approaches will work as intended.

Fixes #6696
Merge pull request #7005 from mrclay/ewinslow-page-handler-bc-b6696

fix(router): Can return 'handler' param in `'route', $identifier` hook again
fix(upgrade): test for ability to connect to localhost if rewrite test fails

Fixes #6888
Merge pull request #7006 from mrclay/beck24-rewrite_error_test

fix(upgrade): test for ability to connect to localhost if rewrite test fails
docs(upgrading): Added upgrade instructions for 1.8 to 1.9

Closes #5900
fix(collections):  make urls work regardless of username

Fixes #6059 - adds a second parameter 'owner' to the url for pages listing collections owned by a user.
Previously the page could not be accessed if the username was 'add'