Add minimal controls for arguments related to assets

[diego-G]

By the time being, lisk-js relais on schema validations from core. Even though, we should implement minimal controls to ensure a proper argument processing inside the application.

I tag the issue as a bug because the application doesn't handle some exceptions properly. For example when using createVote with delegates argument as null. Below the output log:

vote.createVote(account.password, null)

TypeError: Cannot read property 'join' of null
    at Object.isVoteTransaction (node_modules/lisk-js/dist-node/transactions/crypto.js:85:65)
    at getTransactionBytes (node_modules/lisk-js/dist-node/transactions/crypto.js:208:42)
    at createTransactionBuffer (node_modules/lisk-js/dist-node/transactions/crypto.js:339:35)
    at getBytes (node_modules/lisk-js/dist-node/transactions/crypto.js:357:9)
    at getHash (node_modules/lisk-js/dist-node/transactions/crypto.js:386:14)
    at Object.sign (node_modules/lisk-js/dist-node/transactions/crypto.js:410:13)
    at prepareTransaction (node_modules/lisk-js/dist-node/transactions/utils.js:32:31)
    at Object.createVote (node_modules/lisk-js/dist-node/transactions/vote.js:62:40)

[toschdev]

This will be solved by #417 so I am closing this issue