Add screenshots

[orenault]

Add the ability to add screenshots:

• when writing TC, in order to enhance the TC description
• these snapshots should be displayed when running the TC, this will enhance the TP execution.
• when execute TP, add the ability to add screenshot (drag and drop as done in gmail or atlassian JIRA) in order to show defects/issues...

[kinow]

+1 thankfully Laravel has made uploads quite easy. Once we have users from #42 we can create upload areas by user, and also for test cases, test plans, etc.