Deprecate _config.axi.erb in favor of a DSL

[amclain]

By passing a binding to ERB, _config.axi.erb can be replaced by a Ruby DSL or YAML config file, like:

touch_panels:
    ROOM_1: 10001
    ROOM_2: 10002
    ROOM_3: 10003

The current config file is 49 lines long and mixes configuration with implementation.

[amclain]

Issue #2 bumped the version to 2.0, so this issue is being pushed back to 3.0. Although issue #2 cleaned up _config.axi.erb, it would still be nice to redesign it.