Logging and --help updates

[Aleksander Morgado]

Hey Dan, Torsten, and everyone,

The following two patches try to cleanup a bit the current logging and --help setup, before we try to add the optional systemd journal support.

The first patch is just to disable by default the function location information on --debug, and make it possible to enable it with a new --log-func-loc.

The second patch reworks the whole context to make all logging options under the same group, and also updates --help to show all groups by default (i.e. without needing --help-all).

Comments?

[PATCH 1/2] log: new --log-func-loc option to enable function
[PATCH 2/2] context: rework application options and help output