Update to Java 1.7

Closes #77.
Remove dropbox support

We never implemented totally DropBox support and dropbox river has never been updated to recent elasticsearch versions.

For now, we should remove dropbox support and add it again once it will be doable.

Closes #79.
Remove google drive support

We never implemented totally Google drive support and google drive river has never been updated to recent elasticsearch versions.

For now, we should remove google drive support and add it again once it will be doable.

See #79

Closes #80.
Remove JIRA support

We never implemented totally JIRA support and JIRA river has never been updated to recent elasticsearch versions.

For now, we should remove JIRA support and add it again once it will be doable.

See #79

Closes #81.
Remove S3 support

We never implemented totally S3 support and S3 river has never been updated to recent elasticsearch versions.

For now, we should remove S3 support and add it again once it will be doable.

See #79

Closes #82.
Cleanup non implemented options
Update to elasticsearch 1.3.2

Closes #78.