Fix #1284: Regression: Invalid XHTML in shiny exception template when first line in stack frame is HTML. Adds test for this and other issues. Also refs #1009, #1240 and #1242
Allow configuration of prefix for route generation through options, closes #1285
merge 9f30d802ab1246e4796de5093e9be512db72bee4...2f304bd059ff8f6bd95960be05a260597627cac1 (from 1.0)