Fix lookupCommand with multiple addon commands

Previously `lookupCommand` iterated through every addon with commands,
reassigning `addonCommand` for each one. As a result, having multiple
addons with commands installed would clobber lookup of all but the last
addon’s commands.

Now it breaks out of the loop as soon as it finds a matching command.
Merge pull request #2121 from jgwhite/lookup-command-patch

Fix lookupCommand with multiple addon commands
Fix two typos in the ember help generator command output
Add `before` and `after` options to insertIntoFile
Merge pull request #2123 from BastionFennell/master

Fix two typos in the ember help generator command output
Merge pull request #2122 from bantic/add-before-after-options-to-insert-into-file

Add `before` and `after` options to Blueprint#insertIntoFile
Generate pod components within components subdirectory.
Git based app blueprints

Extends `ember new'`s --blueprint option to accept git remotes in
either git@someservice.com:app-blueprint-test.git or
https://someservice.com/trek/app-blueprint-test.git style git remote
urls.
Merge pull request #2103 from trek/git-app-blueprints

WIP: Git based app blueprints
Merge pull request #2130 from kamalaknn/grp-pod-components

Generate pod components within components subdirectory.
Ensure that the app config does not get mutated by addons.
Merge pull request #2133 from rwjblue/ensure-app-config-wins

Ensure that the app config does not get mutated by addons.