Merge pull request #1 from altsai/new-autoflash

New autoflash
Merge remote-tracking branch 'atsai/master'
Updated README.md
Updated the usage message of flash tools
Disable GUI for MAC now. Issue #20 will add GUI for MAC.
Fixed typo
Added nexus4 support for TWCI flash tool
Added file check for shallow_flash and flash_TWCI
Added error handle of download desktop client
Refactoring the auto_flash_from_TWCI
Modified flash "-help" description
Merge pull request #22 from ypwalter/fix_help

Modified flash "-help" description
Merge remote-tracking branch 'atsai/master'
Added new pvt flash tool
Updated naming rule for pvt
Refactoring auto_flash_from_PVT.sh
Updated the dialog layout of flash_pvt
Let auto_flash_from_PVT.sh work now
Updated usage message
Added PVT mozilla-central-unagi-eng build into PVT_DL_LIST.conf