feature/2.2/provide field usable operators

[sensorario]

Q	A
Branch?	2.2
Minor version?	2.2
Hotfix?	no
Refactoring?	yes
New feature?	yes
BC breaks?	yes/no
Deprecations?	no
Tests pass?	yes

This PR contains a little Dictionary refactoring. Dictionary's operators are now splitted in three families:

• numbers
• strings
• fields

The component provide database map to the client with operator that can be used, for each field, to apply a filter. It is called Sherlock just because will helps in searches. It does not commit any search.

For each entity it provide a map with filters and relations

{
    "fields": [],
    "relations": [],
}

Each node will be like this:

"appbundle.entity.entityname": {
    "fields": [
        "id": [">", "<", "=", ...],
        "username": ["contains", "endswith", ...],
    ],
    "relations": [
        "relName": "thebundle.entity.entityName"
    ],
}

[AlessandroMinoccheri]

squash and merge