Enabled the deletion of tables by synching with database every time a table is supplied

[nilsbore]

I have yet to add a flag in the services for if you want to add the changes to the database or not, will add that later in the week. Right now, you can use the detect_tables service which takes a pointcloud as an input and returns tables and corresponding indices in pointcloud (if sub-sampling has been disabled in launch parameters these will be valid).

[cburbridge]

I think the flag is not so urgent, as most of the time when the service is called it wont be to update the database.