Implement Error Trait

[codehag]

Based off the work in #502

This issue is to track moving the error checker trait off of ast builder, and add it directly to the parser.

parts:

• create an error builder trait, that mirrors ast builder trait
• remove error checker trait from ast builder, and use it as the base for an error builder class
• move context_metadata from ast builder to error builder
• add a new trait on the parser