Clean up plugin handling

- no longer vrprint from plugin directly
- improve registration function
- misc cleanups
Rename VR_user_t to struct vrmr_user
Remove unused defines from vuurmuur.h
Introduce vrmr_init() to initialize libvuurmuur
Don't use global conf in backend api calls, rename them to use vrmr_ prefix
Don't use global conf in write_configfile call, rename to use vrmr_ prefix
Make more functions of libvuurmuur use cnf as an arg, instead of global conf.
Make libvuurmuur print funcs unaware of bash out, move logic to vuurmuur
Remove verbose out logic out of libvuurmuur print functions
Rename libvuurmuur log print funcs to use vrmr prefix
Remove libvuurmuur print func dependencies on global conf
Make sure rules_init_list doesn't use global conf
Make iptcap_load_module not use global conf
Make blocklist functions not use global conf in libvuurmuur
Shaping: no longer rely on bash output mode in libvuurmuur shaping func
Remove global config from libvuurmuur
Rename struct ipdata to vrmr_ipv4_data and similar for ipv6
Rename struct options to struct vrmr_rule_options
Rename VrGetString to vrmr_get_string, same for VrGetLenString
Rename VR_filter to vrmr_filter