Introduce user.cljs, plugin.edn, project.clj for user plugins

Rename deploy/core/misc -> deploy/core/settings since all files
pertain to settings.
Rename example.{behaviors,keymap} to user.{behaviors,keymap} so all
source plugin file names match destination file names.
Load user.cljs and its commands

user.cljs commands are loaded through its compiled js
and by adding user plugin to available-plugins. The latter
is needed in order for load-js to correctly find user_compiled.js.
Update user.plugin :dependencies for plugin (un)install/update

It's important to update :dependencies as this allows a user plugin
to contain all information needed to recreate a user's configuration
on another machine.
Trigger off of :refresh! instead of new :save-deps behavior

Relying on explicitly placed :save-deps doesn't handle the case of a user who git clones
a plugin. By triggering off of :refresh!, a user would update their dependencies
just by opening the plugin manager which is highly likely. :save-deps also needed
to be in update-outdated. Triggering off :refresh! solves this.
Fix uninstall causing extra missing popup

Since the user plugin has all dependencies, uninstalling anything triggers
the missing? popup before we've had a chance to remove the dependency from
the plugin.edn. Added a flag to available-plugins to bypass the popup for
just this case.
Add command to open user.cljs
Add command to add user plugin to workspace

Encourage users to explore and understand their settings and a plugin's
makeup
Add some descriptions to user.cljs
Merge branch 'master' into add-user-plugin

Conflicts:
	src/lt/objs/plugins.cljs
move to MIT license
Merge pull request #1703 from LightTable/omm/license

Move to MIT license
Update contributing to pull in contributing intro

Also expanded Plugins section into a more actionable Feature Requests section.
Add quote pair, close #1556
Merge branch 'master' into add-user-plugin
Fixed first-time copy of user.cljs

First-time copy of a user.cljs was currently misplaced causing issues
when behaviors were loaded. Moving it to pre-load resolved this.
Also tweaked command description per feedback
Rename settings/ to User/ and truly fix copying user plugin

Although the previous commit worked, it was by chance since create-user-plugin
and init-plugins were triggering off the same trigger.
Dry up references to user plugin dir
track down the nw11 white screen bug

Signed-off-by: Chris Granger <ibdknox@gmail.com>
merge

Signed-off-by: Chris Granger <ibdknox@gmail.com>
Merge pull request #1684 from cldwalker/add-user-plugin

Add User plugin