remove catmaid_GET/POST/J functions
Add catmaid_get_annotationlist()
read.neurons can have a progress bar

* useful if we are going to download a lot of them ...
catmaid_get_annotationlist returns users per neuron

* also fix typo in egs
fix misunderstanding about nature of annotation list
handle situation where neuron is empty
ensure read.neuron.catmaid uses supplied conn
give read.neurons.catmaid an OmitFailures argument
list2df utility function can index by colnames
Add catmaid_query_by_neuronname
Need to collect skeleton_ids column as well
read.neurons.catmaid has a df option

* also make much prettier worked example
document query argument