V1.3 removed bug (full SRAM)

SRAM in plainDRT and ethernetDRT was full. Devices opearted but did not
logged to SD card. Shortended new added error massages.
Also changed behavior in case of error while writing to SD card: If SD
card is not present on start up, device can be operated without SD card
like in former versions. If SD card was present at startup and error
occurs while writing to SD card during experiment, the device will now
hang forever.