libti*: add support for reading, sending (, writing ?) TI-eZ80 bundle files

[debrouxl]

With the advent of OS 5.3.0 for the 83PCE and 84+CE, TI introduced a new "bundle" format for combined OS + FlashApps upgrades, containing:

• a METADATA file containing, well, simple metadata about the bundle;
• a set of 1 8pu (83PCE) / 8eu (84+CE) file, multiple 8ek FlashApps, multiple 8ca images;
• a trailing _CHECKSUM file

wrapped in a plain ZIP file (that is, it doesn't have a special header, unlike Nspire OS upgrades). The file extension is .b83 for the 83PCE and .b84 for the 84+CE.

Chances are that apart from the metadata, this could be modeled using existing data structures.

Foreseeable tasks:

• libtifiles:
  • add support for the .b83 and .b84 extensions;
  • add support for parsing the ZIP content to (probably) TigContent containing FileContent and FlashContent instances;
  • should support for writing bundle files be added ?
• libticalcs:
  • add support for handling more than one file in calc_84p.cc::send_os_834pce();
  • obtain the OS version before trying to send it again. Maybe we should ask for user confirmation to overwrite even if same version... but that would require splitting ticalcs_calc_send_os() and the underlying functions and data structures, and adjusting the callers;
  • try to do whatever it takes to handle calculator disconnect and reboot properly. Again, if that's made easier by splitting the send OS worflow, so be it ?
  • does TI-Connect CE perform delta updates for FlashApps ? If so, how ? Maybe by using the 0x0031 parameter ID, which I dubbed DUSB_PID_FLASHAPPS... would need a dump to confirm.