Add UpdateTokenPalletTokenConstraintsProposalDetails mappings #550

Job	Run time
MacOS Checks (18.x)	9m 10s
Ubuntu Checks (18.x)	5m 56s
Build joystream/node	38s
Tests (full)	1h 6m 26s
Tests (setupNewChain)	13m 23s
Runtime Upgrade from production runtime	0s
Tests (setupNewChainMultiStorage)	13m 9s
Tests (bonding)	16m 24s
Tests (storageSync)	22m 41s
	2h 27m 47s

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