Add monitors to Fixed Target page to check number of images collected and PMAC status

[noemifrisina]

To monitor the state of a scan for the fixed target, it is useful to check the value of two PMAC PVARS which are saved in the PVs:

• the scan status BL24I-MO-IOC-13:PMAC:read:P2401 - goes to 1 on run program start and back to 0 at the end
• the images counter BL24I-MO-IOC-13:PMAC:read:P2402 - counts the number of images acquired.

There should be a couple of read-only PV monitors on the Fixed Target page.