Add a "reserve" button

[mithro]

Add a reserve button which does the following;

• Marks the FPGA status as being "reserved by until <1 hour from now>"
• Reserve button becomes a "extend reservation" which extends the reservation for another hour.

The reserve button should not actually "do anything" (such as trying to prevent other people from accessing the system or similar), it just changes the status message.

Really simple implementation;

• Touch a file.
• Have cronjob that deletes any file older than 1 hour.