Fix 1182 mixed tech ds do not save ba tech type

[Sleet01]

Fairly extensive overhaul of Transporter bay encoding / decoding to fix MML 1182 so that mixed-tech vehicles with BA transport bays can utilize the correct type and save/load correctly.

Overview:

1. Replaced the current variable-length "Numbers" field encoding transporter bays with fixed-length encoding that uses 6 fields. This simplifies Transporter bay loading significantly (when reading the new format).
2. Moved infantry platoon type and facing to separate fields; previously, either could be found in field 2 or 3.
3. Removed 'f' prefix from the "Facing" data, but still allow each entity type to store arbitrary integers in field 4 as there does not appear to be a set of unified "Facing" values used by all Entities.
4. Made the bay type field (field 5) a bitmap to store various states, e.g. ComStar, Clan, or IS tech base, compactly.
5. Added conversion function to read in older BLK files but store new files in the updated format.
6. Updated all Bay types to output their data in the new format.
7. Added unit tests of the new conversion functions.
8. Added a unit test that verifies that we now save/load data as expected per MML 1182 above.

New bay "numbers" format:

// Field 0 is the size of the bay, in tons or # of units and is required
// Field 1 is the number of doors in the bay, and is required
// Field 2 is the bay number and is required; default value of "-1" is "unset"
// Field 3 is used to record infantry platoon type; default is an empty string
// Field 4 is an int recording facing; default is string representation of entity.LOC_NONE
// Field 5 is a bitmap recording status like tech type, ComStar bay; default is "0"

Compatibility:

• 49.14 BLK file -> 49.XX load: OK
• 49.XX BLK file -> 49.XX load: OK
• 49.XX BLK file -> 49.14 (or earlier) load: Entities with bays will load but some data may be incorrect, specifically mixed-tech BA bay weights (they will all be converted to the base tech type), ComStar BA bays (won't be correct type), and any bays with facings (e.g. in Space Stations).

[Sleet01]

I'll update the PR to fix the above issues tonight.

[NickAragua]

Does this do ok loading both "before" and "after" blk files?
Edit: reading the PR notes, apparently mostly yes.

[NickAragua]

Looks fine, but I'll leave this up for a little bit for others to take a look at as it is fairly extensive.

[HammerGS]

Merging so QA has access to test.