Cleanup invocation of external tools via execute

* avoid unbuffering via "script", and do as much
  as possible from withing python now,
  most specificall:  timeout handling

Conflicts:

	src/settings_local.py
Really apply replacements during file copy
make JAVA executable and PROGRAM name for class containing main available to scriptchecker
export correct JVM setting to environ in ScriptChecker
Allow certain none standard file upload extensions
If chardet detects an unknown encoding, still try the defaults encodings before failing
Pull Output from outtimed checkers before killing them

Prevents truncated output
Revert "Pull Output from outtimed checkers before killing them"

This reverts commit 759b3d96f6c1cb4b2ee717cf8824c8201d3f6a41.
Send TERM to outtimed process before killing it

Thus giving it a chance to flush buffers
Improved Solution Eclipse-Export

* more cleanly seperate user submission from praktomat files
  using eclipse src folders
* ship with autogenerated test-suite for all junit tests,
  together with appropriaye security-managed launcher
Set sourcelevel 1.7 in Eclipse Solution Export
Enhance Attestation-Creation

* Warn Tutor if he is about to create an attestation for a solution for which there already is an attestation
* Display the "next solution" button to create an new attestation for some unspecified user unconditionally
Properly encode autogenerated file when export Solutions as .zip
Do not only display statistics by tutorial, but also by tutor