Add icons showing if people is assigned, GNSS files, logsheet or additional files are attached or not

[demiangomez]

Currently, the only way to see what is present in a visit is to open it. It would be nice to add icons to the left or right of the visit date representing what we have available for it (pictures already appear, so that's good). If a logsheet file is present, then add an icon showing that; if people are assign, show and icon; if GNSS files are present, show an icon, and so on. We should try to represent with an icon at least the following:

• GNSS files
• People
• Log sheet
• GNSS files
• Other files