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

Update mailinglist addresses.
Update index.rst

Typo fix.
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.