In chemlook: enable serach for chemical classes, e.g. 'triazine herbicide'

[andschar]

• Enable cl_query('triazine herbicide', from = 'class'). Searching by lass is currently not supported.
• Fix Error No such column: name in cl = cl_query('Acetamiprid', from = 'name', what = c('class')). This happens b/c the id cols are excluded when not explicitly specifying them in what=