[WIP] allow text and blob indexes

[jycor]

Changes:

• can parse valid queries like create table test (t text, primary key (t(10)))
• throw errors that better match MySQL for blob/text indexes

TODO:

• SHOW CREATE TABLE for tables with index lengths don't show their lengths
• sorts backwards for some reason?
• need a way to only check the prefix length for key collisions
• generated plans should not have filter above indexedaccess