Modernize fastboot output format.

After:

  --------------------------------------------
  Bootloader Version...: 0.5
  Baseband Version.....: 0.5
  Serial Number........: serialv1.0
  --------------------------------------------
  Checking product                                   OKAY [  0.032s]
  Sending 'boot' (9962 KB)                           OKAY [  0.350s]
  Writing 'boot'                                     OKAY [  0.143s]
  Sending 'dts' (14 KB)                              OKAY [  0.068s]
  Writing 'dts'                                      OKAY [  0.048s]
  Sending sparse 'system' 1/2 (460796 KB)            OKAY [ 14.383s]
  Writing sparse 'system' 1/2                        OKAY [  4.138s]
  Sending sparse 'system' 2/2 (443712 KB)            OKAY [ 13.871s]
  Writing sparse 'system' 2/2                        OKAY [  3.246s]
  Rebooting
  Finished. Total time: 36.962s

For a failure:

  extracting android-info.txt (0 MB) to RAM...
  --------------------------------------------
  Bootloader Version...: 0.5
  Baseband Version.....: 0.5
  Serial Number........: serialv1.0
  --------------------------------------------
  Checking product                                   FAILED

  Device product is 'hikey960'.
  Update requires 'marlin' or 'sailfish'.

  fastboot: error: requirements not met!

This change also adds a -v/--verbose flag, but doesn't make much use of
it yet (http://b/30953083 will need it).

Bug: N/A
Test: manual
Change-Id: I7d19f5775859ffad5f3be5707b37dcb6e180917f