Semi-protect admin boundaries by default

[RicoZ]

make it harder to move nodes of administrative boundaries by accident or otherwise damage them. Administrative boundaries do not change very often but are very frequently tied to waterways making them highly susceptible to accidental change.

It may be already possible to achieve a lot with filters - but a one-click solution or rather default-on-protection setting would be preferable for many users.

Also, in cases when admin boundaries and other ways are overlapping it can be very tricky to edit anything without modifying the boundary and filters don't seem to help there.

Related to ​http://josm.openstreetmap.de/ticket/4236