Resolve leftover TODO in Eclipse plugin

[Hjdskes]

These didn't make it in #48, as they require a bit more work.

src/main/java/org/metaborg/spoofax/shell/client/eclipse/impl/EclipseDisplay.java:    // TODO: Use ReplDocument to provide custom partitioning? Perhaps more something for the output
src/main/java/org/metaborg/spoofax/shell/client/eclipse/impl/EclipseDisplay.java:                // TODO: this could mess with the styleranges, perhaps style() shouldn't be called
src/main/java/org/metaborg/spoofax/shell/client/eclipse/impl/EclipseEditor.java:        // TODO: text has been modified, send it to get syntax highlighting.
src/main/java/org/metaborg/spoofax/shell/client/eclipse/impl/EclipseRepl.java:        // TODO: Style input! Output cannot be styled since there is no way to "pretty-prettyprint"