Fixes #12111 Make fine-grained API authorization a plugin

[fanf]

Issue: https://www.rudder-project.org/redmine/issues/12111

The main changes are:

• the ApiAccounKind now holds authorization for PublicApi type, other types don't have specific authz (they are induced by account kind),
• we have 5 ApiAuthorizationKind: None, RO, RW, ACL
• ACL is interpreted only when the plugin is enable. When that kind is used without the plugin, authorization are interpreted as RO (but actual ACL are kept, so that re-enableling the plugin make find back ACLs)
• when migrating from 4.2, authorization are set to RW
• also corrected the logs so that we can have relevant information in debug mode:

[2018-02-16 12:17:24] DEBUG api-processing - Processing request: POST /rudder-web/api/latest/settings/node_onaccept_default_policyMode [JSON request with valid JSON body]
[2018-02-16 12:17:24] DEBUG api-processing - Found a valid endpoint handler: 'modifySetting' on [POST settings/{key}] with version '10'
[2018-02-16 12:17:24] DEBUG api-processing - User 'REST Account: "Test 1" (00000001-379a-4e96-b2e8-b1ac6f7fd4a5)' has RW authorizations.
[2018-02-16 12:17:24] DEBUG api-processing - Handler for 'POST api/latest/settings/node_onaccept_default_policyMode' executed in 27 ms

[2018-02-16 12:17:39] DEBUG api-processing - Processing request: POST /rudder-web/api/latest/settings/node_onaccept_default_policyMode [JSON request with valid JSON body]
[2018-02-16 12:17:39] DEBUG api-processing - Found a valid endpoint handler: 'modifySetting' on [POST settings/{key}] with version '10'
[2018-02-16 12:17:39] DEBUG api-processing - User 'REST Account: "Test" (a92b486d-379a-4e96-b2e8-b1ac6f7fd4a5)' has ACL authorization and a plugin allows to interpret them.
[2018-02-16 12:17:39] DEBUG api-processing - Handler for 'POST api/latest/settings/node_onaccept_default_policyMode' executed in 4 ms

[2018-02-16 12:17:53] DEBUG api-processing - Processing request: POST /rudder-web/api/latest/settings/node_onaccept_default_policyMode [JSON request with valid JSON body]
[2018-02-16 12:17:53] DEBUG api-processing - Found a valid endpoint handler: 'modifySetting' on [POST settings/{key}] with version '10'
[2018-02-16 12:17:53] DEBUG api-processing - User 'REST Account: "ServiceNow" (d5f76fda-a578-47d5-be60-f2174ad56aa7)' has RO authorization.
[2018-02-16 12:17:53] ERROR api-processing - Authorization error for 'POST api/latest/settings/node_onaccept_default_policyMode': User 'REST Account: "ServiceNow" (d5f76fda-a578-47d5-be60-f2174ad56aa7)' is not allowed to access POST api/latest/settings/{key}
[2018-02-16 12:17:53] ERROR com.normation.rudder.rest.RestUtils - "Authorization error: User 'REST Account: \"ServiceNow\" (d5f76fda-a578-47d5-be60-f2174ad56aa7)' is not allowed to access POST api/latest/settings/{key}"

[Normation-Quality-Assistant]

This PR is not mergeable to upper versions.
Since it is "Ready for merge" you must merge it by yourself using the following command:
rudder-dev merge https://github.com/Normation/rudder/pull/1858
-- Your faithful QA

[Normation-Quality-Assistant]

This PR is not mergeable to upper versions.
Since it is "Ready for merge" you must merge it by yourself using the following command:
rudder-dev merge https://github.com/Normation/rudder/pull/1858
-- Your faithful QA

[VinceMacBuche]

OK, merging this PR