Databases work

+ Add IDatabase & IReader to make database access "universal"
+ Changed PostgreSQL class to be a Plugin and implement IDatabase
+ Add PostgreSQLReader class (implements IReader interface)
Databases work

+ Add properties aliases to PostgreSQL class
MM5 plugin and related work

+ Add MM5 plugin
+ Add SensyfPostgreSQLLocalServer plugin
+ Add the RunTimeAssignment class to Tasks, in order to allow search for
tasks from any task (for runtime assignment that depends on value of a
property or node). Required changes in many files.
+ Add 2 tests
+ Changed all the database access and the PostgreSQL plugin was adapted
to the changes