LTI: Replace result on every "Score"

[MrSerth]

Currently, we have two steps for grading a learner's submission: First, a learner clicks "Score" to get feedback and second, a learner clicks "Submit" to send the score to openHPI. This process is cumbersome. We should improve it by sending the result each time a user requested a score.

Initially, scores were only sent once on request (as the LTI parameters were only valid for a single use), but this is not the case any longer. We also reuse the same parameters each time for the RemoteScore action, so the regular browser-based Score should behave similar.