Summary:
The type system is modelled after "CIP2015-09-16"
https://github.com/opencypher/openCypher/blob/master/cip/1.accepted/CIP2015-09-16-public-type-system-type-annotation.adoc
This is needed for registering procedures and their signatures. The
users will be able to specify what a custom procedure accepts and
returns. All of this needs to be available for inspection during
runtime. Therefore, this diff implements printing types as a user
presentable string. In the future, we will probably want to add type
checking through these types, because openCypher requires type checking
on values passed in and returned from custom procedures.
Reviewers: mferencevic, ipaljak, dsantl
Reviewed By: mferencevic
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D2544
