daemon: Change what message of NeighborNotAvailableException
daemon: Handle ConnectionNotAvailableException in queue procedure
daemon: Re-organized exceptions and added throw limitations

There exist two exception classes with the same name. Due to that confusing
construct one of these exceptions was not handled properly. This patch re-organizes
these exceptions and rename both to avoid future confusion.

NeighborNotAvailableException in ConnectionManager renamed to
NodeNotAvailableException

NeighborNotAvailableException in NeighborDatabase renamed to
EntryNotFoundException
Merge pull request #118 from morgenroth/Fix-exception-handling

Fix exception handling due to confusing exception naming