update extension documentation

An extension now has its own page to describe how it works
and the canvas-specific configurations are clearly labeled.

Change-Id: I2a5e5e058b15a903d6231b0344373eff9cbe4e79
Reviewed-on: https://gerrit.instructure.com/20618
Reviewed-by: Brad Humphrey <brad@instructure.com>
Product-Review: Brad Humphrey <brad@instructure.com>
QA-Review: Brad Humphrey <brad@instructure.com>
Tested-by: Brad Humphrey <brad@instructure.com>
fixing broken parser spec

the parser started defaulting privacy level to anonymous instead of nil

Change-Id: Idebd0a58c641c62b19cf8854bb91338facfd165b
Reviewed-on: https://gerrit.instructure.com/20639
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brad Humphrey <brad@instructure.com>
Product-Review: Brad Humphrey <brad@instructure.com>
QA-Review: Brad Humphrey <brad@instructure.com>
support new lti params and iframe embedding

Change-Id: I390ed1acb0cab6efac0dd0ac33d89011e60ef250
Reviewed-on: https://gerrit.instructure.com/20752
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brian Whitmer <brian@instructure.com>
Product-Review: Brian Whitmer <brian@instructure.com>
QA-Review: Brian Whitmer <brian@instructure.com>
Tested-by: Brian Whitmer <brian@instructure.com>
learning registry proof of concept

Change-Id: I97f271a017133208e1dfb34909d5159fa6c2597f
Reviewed-on: https://gerrit.instructure.com/20753
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brian Whitmer <brian@instructure.com>
Product-Review: Brian Whitmer <brian@instructure.com>
QA-Review: Brian Whitmer <brian@instructure.com>
Tested-by: Brian Whitmer <brian@instructure.com>