* refactor: Centralize MIB include directory specification
The default is now:
```
$config['mib_dir'].'/mibdirname:'.$config['mib_dir']
```
This means we exclude OS mibs and only use ours (we could prepend `+` if we want to include os mibs.
All snmp calls should only include the name of the subdirectory under the mibs directory.
* Remove d_echo from Proc
Fix snmpsim tests.
* Proc class
Encapsulate processes in a class, when they go out of scope, we can use the __destruct() process to make sure the process terminates.
* Fix rrdtool_last checks failing
* Don't close rrdtool in rrd_graph
Try to start rrdtool process if they haven't been started yet
Remove some extra debug output
* phpdocs added
several cleanups
should still be functioning the same
Only open one rrdtool process for graph.php
