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to be in update-outdated.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
Allow users to press enter in autocomplete by default. Close #1296

Not being able to press enter in all contexts by default (including autocompletion) is surprising.
Users can still select a completion with tab.
Mention license in readme, close #973
Adjust contributing wording to avoid any misleading wording, close #1614
Fixed couple of compile-time warnings #1658
Fixed couple of compile warnings
Fixed couple of compile-time warnings #1658
Merge branch 'master' into add-user-plugin

Conflicts:
	src/lt/objs/plugins.cljs
Bring back some functions, that might broke inner API
move to MIT license
Encourage users to go the mailing list for questions

A number of issues I've addressed in the past weeks were questions that had a better
chance being answered in the mailing list than being a github issue.
Most recently #1704. Also added a section on what to include on bug reports.
Fix remaining warnings that can be fixed

Outstanding warning is caused by fetch. Did end up removing populate
as it referred to a nonexistant function and couldn't have worked since
it was imported
Fix inline-exception warning properly