Add "Notes" to Airports

[FatihKoz]

Adds capability of having notes/remarks for airports, includes;

New database field Airport Model change CSV Import/Export capability for notes Admin Airports list page change Admin Airports edit page change Default Template Airport show page change Update tests for Airport Import

Closes #1466 (Feature Request)

[FatihKoz]

Ok, I give up on those tests... "Notes" do work fine, tests do not ;)