close #511810: bad rql generated when looking for vocabulary for a relation on an entity which doesn't exist (yet) technical details: * add a graph of linked variables in the RRQLExpression instance * modify rql rewriter to remove relations where an unexistant variable and or a variable linked to an unexistant variable is used. * activate this feature in Entity.unrelated_rql if the entity doesn't exists yet

[system]

db-driver   = sqlite
db-host     = 
adapter     = native
db-name     = tmpdb
db-encoding = UTF-8
db-user     = admin
db-password = gingkow

[admin]
login = admin
password = gingkow