Correct check issue error in client/server mode (issue #459) + exit on check failed + correct another issue on Linux CPU SNMP

glances_globals <-> glances_logging

glances_globals -> glances_logs -> glances_processes -> glances_globals

Fix incorrect kernel thread detection with --hide-kernel-threads

On Synology DSM OS (Linux base), python throws an IOError when open does not find a file.
Previously only OSError was handled, now it handles both the OSError and IOError.

Rely on both methods to get per-CPU stats as a percentage.
Replace the 'homemade' one.

When sorting by 'cpu_times', stats are returned as a pcputimes namedtuple,
with user and system CPU time, so they must be summed before numerical
comparison.

Close #453.

Python's platform.linux_distribution() returns an empty tuple if a Linux
distribution is not part of the '_supported_dists' list.

Add a method to parse the os-release file, the new standard release file,
which replaces the multitude of per-distribution ones.

Also, platform.linux_distribution() is being deprecated and then removed
in future Python releases.

- fix help screen
- whitespace before ‘:’
- missing whitespace around operator
- function name should be lowercase
- class names should use CapWords convention
- fix various misspelling