Add spatial calculus functions to the language

[iduartgomez]

Spatial information and calculus is supposed to have first class support in the declarative logic of simag, just like temporal information and time calculus.

[iduartgomez]

What has been added so far (#12):

• Support location type variables.
• Declare location of entities/classes via special function location.
• Allow assignment of location values to variables in indicative conditional sentences conditions.
• Actions (relational functions) now allow declaring the location (just like time) where the action takes place.
• Added a new built-in move function that can be used in ind. cond. functions in the consequence position to declare movement of entities/cls in a given period of time.
• Query if a certain entity/cls is located at a certain place (in the current moment). Will find out if any first-order condition is met.
• Query all entities/classes located in a certain place (in the current moment).

Thing not yet done:

• Queries for a given moment in time which is not current.
• Queries should find out if an object is located in a certain place by nth-order functions. (that is if p then q; and if q then r; and if r obj a is located at 'x.y.z'; right now only the first-order is checked for, unlike with time calculus).
• Check consistency of movements of objects, and roll-back if necessary. (right now it just appends to the bms log.)
• Allow move as a clause in ind. conditional sentences.