Increase last.fm getting limit to 50

Closes #149.
Add basic clickstream collection

Sometimes noisy, but it works. Needs more fine-tuning.
Fix #136 (half-translucent graphs due to clicking)
Rearrange concatenation blocks in Variables tab
Add random selection from list

Closes #156.
Factor out DEFAULT_LINK_DISTANCE
Unbind hidden graphs when setting graph to display
Include hidden graphs when in isActiveGraph() check
Use setGraph() to set in newGraph() and newDiGraph()
Do not show add node/edge options if graph is hidden
Add adjacency matrix entry lookup
Numericize start and end indices for numeric for

Fixes looping forever if end is passed in as a variable.
Merge pull request #161 from Muon/master

Adjacency matrix access, basic clickstream logging and motley fixes