Incremental Rascal builder does not report older errors again (of the non-stale files)

[jurgenvinju]

We should add a feature that when the compiler is done and has reported the new errors for the stale files, for all other other .tpl files in the stale folder, the errors are read in from the .tpl files and reported again in the console.

This is necessary for the error output of the compiler to be an up-to-date "worklist", for the user. We might have to filter for modules that were recompiled anyway by the compiler, to avoid double reporting.