Support nested selection, DEFAULT VALUES and ON DUPLICATE for insertion parser

[soulstompp]

I found the following comment // TODO(malte): support REPLACE, nested selection, DEFAULT VALUES in insert::insertion

[soulstompp]

I went ahead and moved REPLACE INTO into its own ticket since it seems like it will be pretty different from the other changes mentioned.

[soulstompp]

While working on some of the other points mentioned in the ticket I found I wasn't able to parse ...ON DUPLICATE column = column. This seems closely related to the other changes so it feels appropriate in this issue.