Remove dependency on archlinux specific script for languagetool

The current definition of the languagetool linter depends on it being installed with this [script ](https://github.com/archlinux/svntogit-community/blob/packages/languagetool/trunk/languagetool.sh).
It seems to be better to check a few default locations for the `languagetool*-commandline*.jar` as this is the one needed for vim.
This is the way it is done in [dpelle/vim-LanguageTool](https://github.com/dpelle/vim-LanguageTool) for example and does not depend on a script switching to the commandline jar, if the file is called with an file as argument