add 'go get' in build.pl
small code cleanups
extra log handler per log level
bugfix: line numbers in LineBasedDiffs
  * don't use max for line number in del-delta / ins-delta
  * use the individual line numbers
bugfix: don't add prevEq if afterEq contains the whole text
cleanup diff view
  * server request methods in Backend service
  * move diff html fragments in own directive