Fixed bad object path in relay_geometry().
Short-handed feature.properties to properties.

This will come in handy at some point.
Added link to index.html in the status bar.

It doesn't take much space and I expect that page to be in there forever.
Actually I should include links to the other pages and hide the one that I am
alreay on etc. etc.
Rewrote feature look-up a bit.

It looks worse but I'll need it this way.
Set relay_geometry to handle deleted documents.

That means if B and C both link to A's geometry and I upload with
A._deleted:true, the function will hopefully
i)   set B.GeoJSON to A.GeoJSON
ii)  remove B.GeoJSON_clone
iii) set C.GeoJSON_clone to B._id

(On a side note, the previous commit was missing the entire line where I actually
push the new feature to features. I'll just leave it at that)
Explained a litte what is done because it is complicated.
Changed GeoJSON_clone to stay in the properties collection.

Because it wouldn't show up in the for-in statement.
Changed the way FeatureCollection.crs was handled.

It made no sense anyway to have it defined as a global state.
If the geometry of the deleted document was moved into the feature that was
cloning it, the reference system would have been overwritten by an
uninitialized variable.
Added _deleted as special field indicator.

This is because I have to check the link integrity before posting the documents
in bulk, i.e. when either #revert is pressed or in load_features(). While
unchecking the _deleted property would leave the database intact, I'd end up
with duplicate geometries.
Admittedly this is a very poor way of solving it.