[#42646143] Refactor code between plate and container
[#42646143] Move well to_s in receptacle
[#42646143] Refactoring
[#42646143] Add TubeRack class
[#42646143] Add tube rack spec
[#42646143] Rename well to element
[#42646143] Overwrite []= method to add tube in the rack
[#42646143] Fix plate specs to use container methods
[#42646143] Small fixes
[#42646143] Error if a tube is replaced by an other one in the rack
Replace include Container by is_matrix_of
Merge pull request #80 from maxigit/42646143_create_tuberack_in_the_core

42646143 create tuberack in the core