Added tool to calculate STM32 CRC of a file
More correct Python call in unpackFirmware
unpackFirmware: support new (2.0) pbpack format

In new pbpack file there is no version string (bytes from 0x0C-0x1B),
so that all the remaining parts are shifted by 16 bytes.
We determine that by CRC checking, although it is not very fast.

Also newer firmwares don't contain debug resource map, so we cannot
determine resources' original filenames. We use their numbers (indices)
and checksums instead. Checksums will allow to quickly compare resources
from two different firmwares, for example.
unpackFirmware: also unpack "unnamed" resources (1.x)

In 1.x firmwares, there are two resources in the end of firmware file
which have no corresponding entries in resource map. Original version
of this script would not unpack them. Now we will unpack these
resources as "unnamed" (like in 2.0 firmwares).
typo fix in calculateCrc
Added tool to pack firmware with updated pbpack
Added tool to rebuild resource pack

Uses Pebble SDK.
Currently only supports 1.x version.
updateResources: allow passing ready offset to CRC
prepareResourceProject: minor bugfix with symlink
Merge pull request #4 from MarSoft/master

New pbpack format support and crc calculator tool