added param for timeout, added retries

[dg-shadow]

Description

Added retries param to re-attempt connection to db if timeout occurs.
Also added param for timeout.

Checklist

• Required: Code is auto formatted using clang-format
• Extended the tutorials / documentation, if necessary reference
• Include a screenshot if changing a GUI
• Optional: Created tests, which fail without this PR reference
• Optional: Decide if this should be cherry-picked to other current ROS branches (Indigo, Jade, Kinetic)

[dg-shadow]

Hey. Anyone free to have a look at this?

[v4hn]

Looks good and makes sense.

I approve.

[v4hn]

incidentally, @dg-shadow could someone from Shadow have a look at Kei's sqlite implementation for the warehouse?
#123 (comment)
I believe you would also be relieved to have a lightweight replacement for the mongodb and it should remedy problems like the one you work around in this request.