switch to nested args in viz.yaml

[aappling-usgs]

NEW for fetchData, processData, and visualizeData:
(@lindsaycarr, @jread-usgs, @jiwalker-usgs, @lawinslow)

1. All args given in the args block of a viz.yaml item are passed through by their names to their fetch/process/visualize function.
2. Args in the args block are placed in quotes - i.e., they're all characters, consistent with other fields in the viz.yaml. Convert and/or evaluate them within your functions as needed.
3. fetch/process/visualize functions can no longer expect to be handed a data.info arg
4. fetchData.sciencebase and fetchTimestamp.sciencebase and fetchData.url need their args to be within the args block rather than on the same level as other info for an item.

Example:

# viz.yaml
fetch
  -
    id: Cuyahoga
    location: cache/fetch/CuyahogaTDS.csv
    fetcher: sciencebase
    args:
      remoteItemId: 575d839ee4b04f417c2a03fe
      remoteFilename: CuyahogaTDS.csv
    mimeType: text/csv

# function definition
fetchData.sciencebase <- function(viz.id, remoteItemId, remoteFilename, ..., outfile) {
  ...
}

# fetch.make
cache/fetch/CuyahogaTDS.csv: vizlab/make/timestamps/Cuyahoga.txt
    export R_LIBS_USER=$(RLIBSUSER);\
    ${RBATCH} "--args fun=fetchData funargs=list(viz.id='Cuyahoga',remoteItemId='575d839ee4b04f417c2a03fe',remoteFilename='CuyahogaTDS.csv',outfile='cache/fetch/CuyahogaTDS.csv')" \
    vizlab/make/callFunction.R vizlab/make/log/fetch/Cuyahoga.Rout

based on recent use cases and discussion in #5

[coveralls]

Coverage remained the same at 0.0% when pulling c36d356 on aappling-usgs:master into c4a2722 on USGS-VIZLAB:master.

[lawinslow]

args block seems good to me.

[lindsayplatt]

Sounds like we are good to merge @aappling-usgs ?

[aappling-usgs]

great, let's do it.