Prevent actions on regions when it is already deleted from AreaShop

When a region is deleted with '/as del' it wil set a flag in
GeneralRegion to indicate it is deleted (isDeleted() can get it). If
this flag is set then no sign updates, saves to disk etc are being
processed by the tasks anymore. This prevents the following case: #1
task starts saving regions (makes copy of region list). #2 User 
executes '/as del' for a region, removes region file. #3 Task arrives at
the region the user just deleted and saves it to disk again #4 The
region will get loaded again next time the server starts.