Explicit definition structures of route attributes

Explicit definition structures of route attributes

Changes in internal API:

* Every route attribute must be defined as struct ea_class somewhere.
* Registration of route attributes known at startup must be done by
  ea_register_init() from protocol build functions.
* Every attribute has now its symbol registered in a global symbol table
  defined as SYM_ATTRIBUTE
* All attribute ID's are dynamically allocated.
* Attribute value custom formatting hook is defined in the ea_class.
* Attribute names are the same for display and filters, always prefixed
  by protocol name.

Also added some unit testing code for filters with route attributes.