Add inotify support for the new input requirements

1) Monitor a directory for new files written/closed
2) Move the file off to a tmp directory
3) Process the file
4) Delete the file
Move the read functionality into the TelemetryRecord

This allows the data to be read and transformed in a single buffer.
Switch the histogram definition key to char*

Using a char* key in the definition map will avoid tens of thousands
of string constructions/destructions per second.
Trap HUP, INT, TERM, USR2 signals and shutdown cleanly
Don't overwrite the input_directory element even though it is being discarded.