Fixed the problem when a user/space is created with the same identifier of another

When a user or a space are created the system try to create his room using the username/permalink like param. This can result in a error, because the room can't be created with a param equal to another. To resolve this issue a validate function was created in user/space model to verify if doesn't exist another model with the same identifier. If another identifier is found the model aren't created.

Fixed #1071
Adjustments and more tests after PR #9

Main changes:
* Validating the permalink and username on update too, since we don't properly
  block the user from changing these values yet.
* Brought back the check for errors on the bigbluebutton_room when validating
  a space. This should be reviewed, improved, and done for User too.
* Doesn't auto-suggest usernames on 'create' anymore, only on 'new', otherwise
  we might be overriding a value set by the user.
* Improved the js method to generate slugs more similar to slugs valid for
  usernames and permalinks.

refs #1071
Initial changes to allow users to select the default layout of a room

A space admin can have the rights to change the default layout of the room associated to this space. To do that was created a new page in space admin options tab to let admins control the room options.

Refs #960
Remove xmpp server's config files, now on mconf/mconf-chat-server
Remove duplicated js include for select2
Created a new way to allow users to select the default layout of a room

Before this modification was impossible to change the layout of a room, all rooms were presented with the same default layout. Now the idea is to let owners/admins choose from a pre selected list of layouts. For do this was inserted in the configuration pages  of the room (space and user rooms) a new field who owners/admins can select the default layout to be used.

Fix #960
Set the correct sender mail on devise

Devise was using a wrong mail because it was never properly configured.
Has to be the same email used to send the other emails sent from the application,
that's taken from `Site.current`.
Adjustments to set the layout of a room, functional now

Updated bigbluebutton_rails and bigbluebutton-api-ruby to version that now
have it working.
Made small adjustments in the views where the default layout is set in a room.

refs #960
Update bigbluebutton_rails and fix tests

#960 should be done now. Tests are all passing.

refs #960
Merge pull request #13 from mconf/960-default-layout

Conflicts:
	config/locales/en/_simple_form.yml
	config/locales/pt-br/_simple_form.yml
Add .bundle/ to .gitignore
Update bigbluebutton-api-ruby

Fixes merge of PR #13

refs #960
Let the user select empty option for the default layout

refs #960
Update bigbluebutton_rails and bigbluebutton-api-ruby

Includes fixes for setting the default layout using the config.xml.

refs #960
Generate BigbluebuttonRoom#room_options in the migrations

Also updated bigbluebutton_rails and removed the default layout to be
empty and not 'Default'. Empty means that the default layout from
BigBlueButton/Mconf-Live will be used.

refs #960
Fix db:populate, was failing generating Space#permalink

Wasn't generating the permalink properly and was failing when saving spaces.
Made also some other smaller improvements.
Re-enable and improve select2 visually

It was mistakenly disabled by 71768bc35e
Also made it look better, especially in the view invites/invite_room
that was looking pretty bad after it was changed to use select2.
Fix private message text for webconf invitations on v2

The same that was done in the master branch on 07dfa4cbc99c6b.
Wasn't sending the message written by the user when sending the invitation
via private message. Via email was sending it correctly.

refs #1020
Fix wrong language in space invitation emails

The same that was done in the master branch by e3ebbc466756b17.

Was sending the message in the wrong language in some cases, and in some cases
using more than one language in the same email.
This was in the email sent to the admins of a space confirming that a user
accepted or rejected an invitation to join the space.

refs #984
Small adjustment in users/edit so errors are better displayed