TrustingPeriodFraction should be a fraction

[shaspitz]

Problem

#393 made this parameter an sdk "param". But it has always existed as an integer, acting as a denominator to calculate trusting periods. This param makes more sense as a fraction, but will require a way to encode a numerator and denominator into json on genesis.

We could try using ibctmtypes.Fraction or two separate params for numerator and denominator

Related to this, the default for the new fraction should be 2/3 per https://github.com/cosmos/ibc-go/blob/main/docs/architecture/adr-026-ibc-client-recovery-mechanisms.md, i.e.,

we recommend that the trusting period for the 07-tendermint client be set to 2/3 of the UnbondingPeriod.

Closing criteria

Make this param a fraction, be able to encode that fraction in json, set new recommended default

TODOs

• Labels have been added for issue
• Issue has been added to the ICS project

[mpoke]

Alternatively, we can use the same approach as for ConsumerRedistributionFrac.

[shaspitz]

Alternatively, we can use the same approach as for ConsumerRedistributionFrac.

Ah yes, this seems best 👍

[danwt]

I would suggest a 'scalar' or 'multiplier' in [0,1] or whatever appropriate interval.

[jtremback]

Yea, ConsumerRedistributionFrac is a stringified decimal eg "0.75"