if TemplateSyntaxError: display templateName, lineno & highlight error

adds DebugLexer, DebugParser and "origin" to a lot of classes
needs massive unit tests
improve error page

i should think about using a template for that
offbyone; simplify
simpler
cleanup & finish debugging

 * seperate middleware with template
 * proper switch in Environment
 * cleaned some unit tests
 * fixed template origin not always created
improve error messages

sometimtes by removing info because it's duplicated in `Origin`
use context.renderValue in DebugVariableNode

always use this to deal with escape or not
run most tests twice: once with debug and another run without
documentation
add first and last filter
TOC and minor cleanup in README
clearer
Merge branch 'debug' of https://github.com/oberhamsi/reinhardt
Merge branch 'docs' of https://github.com/oberhamsi/reinhardt