public / sequelize

add dialect checks for upsert support

Upserts in MSSQL are non-trivial to implement, adding the ability
to test for support is a valid stopgap for later implementation

stop sequelize from erroneously adding timezone to raw query dates

Only for rawSelects it seems that Sequelize forcibly adds timezone
information to dates returned from the database. This breaks in
strange and magical ways

…(committed or rolled back), closes #2082

add default implementation for upsertQuery

Some dialects developers might need to be reminded they need to
implement the upsertQuery.