Add support for version1 boxes.

[varsill]

This PR:

• adds support for parsing boxes based on the version field
• adds parsing of co64 box
• allows to specify separately field and the mask in the :when clause of the parser

[mat-hek]

maybe the API could look like

modification_time: {:uint32, when: {:version, value: 0}},
sample_offset: {:uint32, when: {:fo_flags, mask: 0x800}}

we wouldn't have to support passing both at the same time