Notify users when the metadata used in their analysis change

[josenavas]

trafficstars

We have the functionality to update the metadata template. However, if a user has used that sample template in their analysis, we have no way to notify the user that the metadata shown in that analysis is an old version.

Some thoughts: add a new status of the analysis, so we know that uses old data. Send an email to the user notifying that. Have some kind off notifications system in the main page, like "your Qiita" were we have something like 'notifications' and we have a list in there.

[squirrelo]

Messaging added in #1244