Collator for the "adder" (formerly basic-add) parachain and various small fixes (#438)

* update basic_add wasm

* wasm feature and collator feature

* move test parachains around a little

* fix wasm build for basic_add

* move basic_add to adder, introduce README

* minimal basic_add collator

* ensure collator messages are sent in the right order

* more logging

* route consensus statements to all peers

* minor bugfixes for parachains

* genesis builder accounts for parachain heads

* fix parachains tests

* targets for txpool

* tweak runtime + collator

* fix version in adder-collator

* consistency for overflowing

* adjust comment

* fix stable test run

* remove dummy registration test

* final grumbles