Fix some problems with domains API.

This fixes a problem where you add a domain via the API and choose to also
add an IP with it. The ip_add_update() handler requires that you pass an
ip_type that is not None. Fix this by taking an ip_type parameter in the
POST data and passing it along.

Another problem is that the handler would not error out early if there
is no source provided. This would cause a validation error later on.

Also, fix some whitespace problems.
Update documentation.
Fix ip_add_update() for invalid ip_type.
Fix actor creation is no source is provided.
Fix actors handlers with missing source.
Merge branch 'master' into domain_ip_api
Fix documentation (Address - ipv4 addr).
Fix for the documentation fix.
Fix API submission failures.

Make the handler bail early if there is no source.

Most of the handlers return messages in the 'reason' key, while only
one returns both 'reason' and 'message' keys. They are now combined
properly.
Another missing source check.
Make indicator handler check for source.
Make IP addition check for source.
Make PCAP handler check for source.
Make raw_data handler check for source.
Fix bug in previous commit.
Make Sample handler catch no source.
Set tag_list to an empty list by default.

This was triggered when adding a screenshot through the API with no
tags. It would throw an exception because tag_list was passed in as None
here.
Update documentation to note "description" on screenshot.
Fix target handler when called from API.

This handler assumed that data was always fully populated, which is not
always the case when using the API. Fix it by checking for the existence
of a key before setting the attribute.
Merge branch 'master' into domain_ip_api