Find a way to shrink or split OOS logs

[sanderd17]

OOS logs are getting too big to work with.

Logs of long games (when there are a big number of units) can't be opened with all text editors anymore, and there's certainly a problem with certain diff tools (like meld).

Some things could be optimised:

• TechnologyTemplateManager shouldn't serialise any data (it can always load the techs from disk when rejoining). r18100
• SerializeVector is very ineffecient; it stores the name of the array with every element, which results f.e. in a lot of lines like

    los state: 0
    los state: 0
    los state: 0
    ....

Next to optimising the OOS log, it could also be split. F.e. one log for the SYSTEM_ENTITY (which currently takes up 25% of the entire log), and then f.e. a log per 1000 or 2000 entities

[sanderd17]

In 18100:

Rename TechnologyTemplateManager to DataTemplateManager in order to reflect its new function. Fixes #3909. Disable serialisation of technology templates. Refs #3834