PROPER multiple account support for the same ID

like right now it's really annoying if you want to switch between multiple accounts you have to switch between multiple masterseeds

technicality suggestion:
```js
"masterseed": {
"certs": {
"issuer.bit": {
"auth_address": "",
"auth_privatekey": "",
},
```
should turn the object of issuer into array then object
```js
"masterseed": {
"certs": {
"issuer.bit": [
{
"auth_address": "",
"auth_privatekey": "",
},
//...
],
```
so users can have multiple ids of the same issuer, useful for sites like milchan which is anonymous orientated

Why?
because for so long we been switching using multi user, for once maybe we should finally have a proper solution for this