Made list of variables to query (trstr) optional in query.priors. Now defaults to NULL.
Generalized variable options for get.trait.data:

Added trait.names as optional arguement. If NULL (default), the code will grab all the priors for a PFT. If TRUE, the code will load and use the trait.dictionary. If a list of variable names, the code will grab just those variables.
Merge pull request #75 from mdietze/master

Generalized get.trait.data to make trait.dictionary optional