Allow long choices to span multiple lines.

Some of the choices for Stewarships and Alerts are long strings. For
example: "Mulching, adding compost, or amending soil." These don't fix
on a single line of a tableview cell. Here we allow the line to wrap.
This might need to be revisited if there are even longer lines, which
would require actually increasing the size of the cell. But it is a fine
solition for the data we currently have and expect in the near future.

Fixes issue #194.
Fix crash when the address string is Null.

Due to some clean-up associated with work done for Stewardship and Alert
searching I pulled out a check to see if an NSString was actually an
NSNull object. This shouldn't ever really happen so it seemed like the
code could have been cleaned up. However due to the way we handle JSON
responses from the API we actually did have a NSNull object sitting in
string space which caused a crash. The compiler doesn't like seeing
objects of different types in direct comparison. So instead we check the
type of the object in the dictionary directly and only if it is not
NSNull do we pull it out and store it on the string.

Fixes issue #197.
Provide a no data message cell.

When there are no stewardship or alert entries, we were just showing a block of
gray with no lines between stewardship, alerts, or ecosystem benefits.
Instead we add a cell that provides a no data message to the user when
on the tree detail page and not in edit mode.

Fixes issue #196.
Merge pull request #199 from lliss/topic/stewardship-display-issues

Topic/stewardship display issues