Doesn't parse multiple variables with the same key

[ideasman69]

Hi there,

This is pretty similar to #169 but rather than not parsing multiple keys with the same name (which has been fixed 😄 thank you!), this one is highlighting the inability to pass multiple variables with the same key name.

For example - a simple dashboard with a variable dropdown that allows the user to select multiple items. If a single variable is selected, it's passed through as expected:

url:"api/datasources/proxy/1/metrics?id=1212"

However, if a second variable is selected - the subsequent varible gets appended to the first id= key, rather than getting it's own id= key in the query:

"api/datasources/proxy/1/metrics?id=1212,1213"

Obviously depending on which advanced variable format option is selected, the query changes slightly but I can't find one that adds an additional id= key per variable which is what the destination API is expecting:

"api/datasources/proxy/1/metrics?id=1212&id=1213"

Just wondering if one of you clever people are able to make a simlar change to #169 but for mutiple variables 😊

Thanks!