More fixes inter alia for move to reshape2

### This fixes

 1. corrects some things that got munged in earlier pull
 2. fixes `get_publications()` following move to **reshape2** plus some other bugs
 3. fixes `get_download()` following move to **reshape2**

### Some explanation

#### `get_publications()`
There were some lines at the end of `get_publications()` that either didn't do anything or were killing the lists or multiple authors. In this pull request I fixed these and in fixing something left over from the move to **reshape2** I reinstated the documented behaviour. However, this behaviour can result in a lot of mainly unused colums when, for example, there is a single publication with many authors. In that case, each row has as many columns in the Author info as the publication with the largest number of authors (multipled by 3 as there are multiple variables per author).

I wonder if it would be better to pull this author information out from the main data frame and return it in long format with a variable for `Publication ID`. It would then be possible to link from this component to the main data frame using the ID. This would involve returning a list with the following components

 1. `publications`; the main data frame returned now, minus the `AuthorX.X.X` components
 2. `authors`; a data frame in long format with the author data and a `PublicationID` variable.

#### `get_download()`

In fixing this for the move to **reshape2** I noted a couple of issues, one of which I have tried to effect a fix for. In the examples for `get_download()` we have

    #' #  Search for sites with "Thuja" pollen that are older than 8kyr BP and
    #' #  that are on the west coast of North America:
    #' t8kyr.datasets <- get_datasets(taxonname='Thuja*', loc=c(-150, 20, -100, 60), ageyoung = 8000)
    #'
    #' #  Returns 3 records (as of 04/04/2013), get dataset for the first record, Gold Lake Bog.
    #' GOLDKBG <- get_download(t8kyr.datasets[[1]]$DatasetID)

When forming the `counts` component, the `TaxonName` may not be unique. For example, in this data set `Lycopodium tablets` occurs twice in `TaxonName`, differentiated by the units field. However, we wish to crosstab on the `TaxonName` variable. When we do that, `dcast()` (and `cast()` before it) would return the data using `fun.aggregate = length` - i.e. count how many times each element of `TaxonName` was present in each sample. This probably went unnoticed because this call was wrapped in `suppressMessages()` and also perhaps not all data sets have non-unique `TaxonName` values.

From the example it seems Simon was aware that more than juts Pollen counts would be in the `counts` component, but if this NeotomaDB doesn't enforce unique values in `TaxonName` then **neotoma** needs to handle this. What I did here was pull out only the the rows where `TaxaGroup == "Laboratory analyses"` and use those for the `counts` component. Then I added a new component `lab.data` which pulled out those rows that matched `TaxaGroup == "Laboratory analyses".

This is clearly inelegant - what other values might there be in `TaxaGroup`? Should we expect to retrieve them all?

I think it is safe to  merge this as it gets these functions working again. I will open issues for each of `get_publications()` and `get_download()` to host discussions on how to proceed with improvements down the line.