Build date

[m-kozlowski]

This change makes managing ota updates of different builds of the same version (i.e. 1.13.6-dev) a little easier. Sample output is:

ESPurna OTA Manager v0.3

  #  HOSTNAME        IP               MAC                APP           VERSION       BUILD_DATE            DEVICE                     MEM_SIZE  SDK_SIZE  FREE_SPACE
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
  1  ALEXA-BRIDGE    10.1.5.151                                                                                                       0         0         0
  2  ESP-RS-01       10.1.22.201      84:F3:EB:83:9F:0F  ESPURNA       1.13.6-dev    2019-05-20 00:32:55   MPK_RS_4CH                 4096      4096      2654208
  3  ESP-WP-01       10.1.22.1        BC:DD:C2:23:2B:E3  ESPURNA       1.13.6-dev    2019-05-20 00:05:06   BLITZWOLF_BWSHPX           1024      1024      516096
  4  ESP-WP-02       10.1.22.2        BC:DD:C2:2A:D5:B3  ESPURNA       1.13.6-dev    2019-05-20 00:05:06   BLITZWOLF_BWSHPX           1024      1024      516096