Multisignature transaction sets property with incorrect casing for multiMin and multiLifetime when applying/undoing transaction.

[SargeKhan]

Expected behavior

The properties defined for account related to multisignatures should be in camel case.

Actual behavior

The multisignature transaction assigns these properties to account in lower case.

Steps to reproduce

Compare code with core.

Which version(s) does this affect? (Environment, OS, etc...)

2.1.0

[shuse2]

It should update to

readonly multiMin?: number;
readonly multiLifetime?: number;