document dev:true in configs, and high level dev documentation

[breezykermo]

For development, setting this flag to true will bypass mtriage's error handling mechanisms so that you can see what's buggy about your selector or analyser.

This should probably come along with a document that explains at a high level all the things you need to know about developing new components, such as the lifecycle API.

[breezykermo]

The fix for this can also include some scaffolding functionality for new selectors and analysers:

• ./mtriage dev new selector
• ./mtriage dev new analyser

Both should create empty components with comments explaining the parts of the lifecycle. This could serve as an effective substitute for more extensive documentation on how to create custom components.