Test build for aliases rework

A very unstable Skript version, for people who want to develop new aliases. See README for instructions.

DO NOT run this on public server! Be prepared to delete your variables database frequently, it will probably get corrupted when updating.

Current build has been tested on 1.13 only. Older versions (1.9+) will continue to be supported in future, but at the moment they are unlikely to work.

Notable changes:

• Reworked entire aliases system
• Changed item variable storage format (upgrade is possible, downgrade isn't)
• Removed support for numeric ids
• Probably fixed some bugs
• But added more bugs

Currently, this test build is mostly based on 2.2-dev37c. It will, when aliases are a bit more complete (transportation category, mostly) become 2.3-alpha1.