MB-16118 : Keep error messages less technical

https://issues.couchbase.com/browse/MB-16118
1. Was trying to create my first index on cbft. Attaching screenshot. The error message makes complete sense but since not every user can interpret a JS regex (^[A-Za-z][0-9A-Za-z_-]*$), can we consider breaking down into rules like -
name must start with an alphabet
must not contain spaces or spl characters than_,-
2. Also if the UI is bootstrap based, can we add dynamic validation for fields, i.e, why wait for user to click on create index to throw "invalid name"?
3."Create index" is enabled by default. No mandatory fields present either.
3. Tried to tweak some plan params, got a "json: cannot unmarshal number into Go value of type blance.HierarchyRules". No clue what this means. Can these json exceptions be wrapped into more meaningful messages?