Entities layer(WIP)

[quesnel]

This project should propose in Irritator a modeling and simulation layer of entities (discret objects) to develop SMA-like models.
This layer is made up of specific models and events. The list of models is as follows:

• entity generator: create entity with name, priority and optional attributes
• entity terminator:
• entity queue:
• entity replicator:
• entity resource acquirer: block entity until resources available.
• entity input switch: select entities according to specific rules.
• entity output switch: select entities according to specific rules.
• entity gate: block entities until control authorization.

These models exchanges these entities via DEVS events. These events are different from irt::message (a vector of four real in the continuous layer):

enum class data_type : i8 {
	integer,
	real,
	string,
};

union data_value {
	i64 integer;
	f64 real;
	small_string<7> string;
};

struct attribute {
	small_string<7> string;
        data_value value;
        data_type type;
};

struct entity {
	small_string<7>  name;
	small_vector<attribute, ??> attributes;
	i8 priority;
};