posts: admin: do not clear the lat and lng.

This is the first patch of the serie that improves the user experience,
by the cost of extra traffic/api_query.

We don't want to clear/nullify the latitude and longitude, rather
preserve it. This change make sure we don't loose the coordinates on
changes within the geo-my-wp metabox in admin area.

Signed-off-by: Anton Arapov <arapov@gmail.com>
posts: admin: do not change the Tab after map pointer drag-n-drop.

It's bad practice to do anything like that instead of user. As well as
Tabs is the one of the gui paradigm that should be avoided when
possible to make the interface clean.

Signed-off-by: Anton Arapov <arapov@gmail.com>
posts: admin: Remove the alert on success.

We should be optimistic, we never fail. Rather give more explanation on
fail and explain what to do, keep silence otherwise. Silence is golden.

Signed-off-by: Anton Arapov <arapov@gmail.com>
posts: admin: change the default center lat/lng to Prague.

Just be in EU. No offense. :)

Signed-off-by: Anton Arapov <arapov@gmail.com>
posts: admin: update lat and lng after map marker moved

We don't want to do an extra step to figure out the latitude and
longitude. Just update the lat and lng once we moved the marker.

Signed-off-by: Anton Arapov <arapov@gmail.com>