Add filter planning support to DBI quadstore

[kasei]

Add SARG and simple filter pushdown support to the query planning in AtteanX::Store::DBI (#73). This can include:

• SARG pushdown:
  • Type restrictions
  • STRSTARTS
  • STRENDS
  • CONTAINS
• BGP Extension:
  • STRLEN
  • UCASE
  • LCASE
  • Hash functions

[kasei]

Closing this after moving it into the kasei/atteanx-store-dbi issues list.