Make SimpleDataBinder handle multiple indexers

[Kernvirus]

Feature description

Hello,

SimpleDataBinder uses this regex to parse the indexer and it's value from a value it wants to map:
static final INDEXED_PROPERTY_REGEX = /(.*)\[\s*([^\s]*)\s*\]\s*$/

But this regex will always choose the last indexer when there are multiple present. Example:
propName = 'columns[0]['data']'
will be matched as

indexedPropertyName = 'columns[0]'
index = 'data'

I'd argue that this is wrong. A groovy property is not allowed to be named columns[0] anyways (right?) so matching that makes no sense. It should instead consider the first indexer as the indexer that matters. It should be:

indexedPropertyName = 'columns'
index = '0'

It would be easy to change the regex to pick the first indexer instead like so:
^(.*?)\[\s*([^\s]*)\s*\]\s*
but I'm not sure if that would break anything and if that's enough to properly support nested indexers. Is this a feature the SimpleDataBinder should support? Since fields that have [] in their name are probably very unlikely to exist, making this change may not be that breaking in real usage.

[jdaugherty]

It's my understanding that the databinder will recurse on the properties as they're added so this will likely break nested lists. If you'd like to submit a pull request demonstrating this change with a test for nested lists, we can certainly proceed with this ticket.