[front-end] Handle errors in metamask actions

[balinskia]

We need to handle actions such as:

• user rejects the transaction
• user doesn't have enough ethers for paying for the transaction
• timeout

A popup would be nice for it

[balinskia]

gatherCollateral(shortId, amount).then(()=>{
   commit('COLLATERAL_TRANSFERED', { shortId });
   onSuccess();
}).catch((err: Error)=>{
  console.error(err);
  commit('SOME_GENERIC_ERROR_PAGE', { msg: "Transferring collateral failed. Do you have enough funds?" });
});