Add binary file format

Add a simple, but flexible binary file format. Also add some command line options to specify the format and the ability to flipV (maya uses y-up for uv).

The file format consist of a header and a bunch of data blocks:

The header is always 32 bytes of which the first 4 bytes contain the file tag "G3DB" and the second 4 bytes the file version. The rest of the header (24 bytes) is reserved for future usage and set to 0.

A data block starts with one byte, the 6 lsb specify the type of block, the 2 msb specify the size of the next value (1, 2, 4 or 8 bytes) which specifies the size in bytes of the rest of the block. Data blocks can be nested, resulting in pretty much the binary version of the json file.