Plugin License not consistent

[jpfr]

Hey all,

we are not consistent with respect to the plugin licenses.
In the Readme we write:

The plugins, as well as the server and client examples are in the public domain (CC0 license). They can be reused under any license and changes do not have to be published.

Looking into the plugins folder, this is no longer the case.
The following files are under the MPLv2:

$ grep -r -l Mozilla
ua_pubsub_ethernet.c
securityPolicies/ua_securitypolicy_basic256sha256.c
securityPolicies/ua_securitypolicy_basic128rsa15.c
securityPolicies/ua_securitypolicy_basic256.c
ua_pubsub_udp.c
include/open62541/plugin/historydata/history_database_default.h
include/open62541/plugin/historydata/history_data_backend.h
include/open62541/plugin/historydata/history_data_gathering_default.h
include/open62541/plugin/historydata/history_data_gathering.h
include/open62541/plugin/historydata/history_data_backend_memory.h
historydata/ua_history_data_backend_memory.c
historydata/ua_history_database_default.c
historydata/ua_history_data_gathering_default.c

And these are under CCZero:

$ grep -r -l CCZero
ua_pki_default.c
ua_nodestore_default.c
ua_accesscontrol_default.c
securityPolicies/ua_securitypolicy_none.c
ua_debug_dump_pkgs.c
ua_config_default.c
ua_log_stdout.c
include/open62541/client_config_default.h
include/open62541/server_config_default.h
include/open62541/plugin/log_stdout.h
include/open62541/plugin/accesscontrol_default.h
include/open62541/plugin/pubsub_udp.h
include/open62541/plugin/securitypolicy_default.h
include/open62541/plugin/securitypolicy_mbedtls_common.h
include/open62541/plugin/pubsub_ethernet.h
include/open62541/plugin/pki_default.h

The files under the MPL v2 are self-contained functionality and unlikely to be changed by an end user. But we need to be consistent. Either ask the authors to make them CC0 or fix the documentation.

Any way, we should be consistent in our categories. So that users can easily infer the license without looking at each file individually.