Add support for index types (bitmap, reverse, etc...)

Hi all,

we are using Liquibase through the liquibase-maven-plugin for our new developments and we are very happy about it. It’s a wonderful piece of code.
However, we need to create reverse indexes and bitmap indexes and it seems that Liquibase do not currently support them. That’s a real pity because we are forced to manually modify the generated sql by Liquibase.
Do you have plan to introduce this feature?
Could be something like this: