Add a csv plain text importer, closes #2689

.meteor/packages

.meteor/versions

packages/rocketchat-i18n/i18n/en.i18n.json

packages/rocketchat-importer-csv/.npm/package/.gitignore

packages/rocketchat-importer-csv/.npm/package/README

.../rocketchat-importer-csv/.npm/package/npm-shrinkwrap.json

packages/rocketchat-importer-csv/main.js

packages/rocketchat-importer-csv/package.js

packages/rocketchat-importer-csv/server.js

packages/rocketchat-importer-hipchat/main.coffee

packages/rocketchat-importer-hipchat/server.coffee

packages/rocketchat-importer-slack/main.coffee

...ocketchat-importer/client/admin/adminImportPrepare.coffee

.../rocketchat-importer/client/admin/adminImportPrepare.html

...cketchat-importer/client/admin/adminImportProgress.coffee

packages/rocketchat-importer/lib/importTool.coffee