Move tags from traits to CivEffect

[Nightinggale]

As mentioned [url=https://forums.civfanatics.com/threads/imperformat-coding-many-trait-modifiers-bypass-processtrait-work-in-progress.673688/]here[/url], traits aren't cached properly. Instead they are often looped, which is bad for performance. Since traits changes rarely, it's an ideal candidate for caching for performance gains.

Moving the tags to CivEffects will allow using the existing CivEffect cache system. It will also allow other CivEffect granting features to make use of the traits.

Known candidates for caching
[x] getLearningByDoingModifier d3e5f01
[] getLearningByDoingFreeModifier
[] getLearningByDoingRunawayModifier
[] getLearningByDoingRevoltModifier
[] iDomesticMarketDemandModifier --> James Lancaster
[] iRecruitPricesModiferAfrica --> Otto Friedrich von der Groebem
[] iRecruitPricesModiferPortRoyal --> existing Pirate (e.g. Captain Henry Morgan)
[] iCapturingSlaveChanceModifer --> existing Conquistador (nor sure yet)