Update manual install

* update extract section extract section was missing download instructions. Added more complete instructions.
* formatting
* Note about requiring terminal, further formatting
* Updated Ubuntu environment install command
* Note formatting
Update index.rst

Typo fix.
Update index.rst

Typo fix.
Update index.rst

Typo fix.
Update index.rst

Typo fix.
Merge pull request #313 from wakeup/master

Update index.rst
Fix external API sample
Merge pull request #315 from owncloud/api-sample

Fix external API sample
Merge pull request #277 from owncloud/manual-install

Manual install
Fixed broken links.
Minor typos - port of #317
Update contact app images and text for new version
update client manual link
Update mailinglists
Merge pull request #320 from owncloud/new-contact-update

Update contact app images and text for new version
adding documentation about asset management in ownCloud
adding documentation about asset management in ownCloud
Set maintenance mode before upgrade.
Disable maintenance mode after upgrade.
Merge pull request #329 from owncloud/upgrade-set-maintenance

Set maintenance mode before upgrade