Fix `--modules-list`

Glances as system tool is often executed in a multi-user environment or
even with root privileges. Then, make the log file system-aware as well.

Change the IRQ shortcut key from R to Q. R is alread used for the RAID plugins. Also update the docs for the IRQ plugin. Last but not leat, change the ReadTheDoc theme

This patch introduces a new export method for sending metrics to
__Riemann__ server using _TCP_ protocol. The module can be enabled like
all the other exports in __Glances__, specifying the `--export-riemann`
option.

Sending metrics to Riemann requires
[bernhard](https://github.com/banjiewen/bernhard) that is
the most popular _Riemann client_ written in python.

In the configuration file you can only specify the `host` and `port`
that riemann is listening for new connections on. Later new options are
planned to be added like __SSL__ support and __UDP__.

Documentation and manpages are refreshed according to the modifications
in the config options and introducing the usage of Riemann export.
Signed-off-by: NGergő Nagy <grigori.grant@gmail.com>