Introduce new env var `LTP_JAR_DIR_PATH` to let the user specify a custom installation path of LT

[pidefrem]

Fixes https://github.com/jxmorris12/language_tool_python/issues/84 Fixes https://github.com/jxmorris12/language_tool_python/issues/82

At the moment, language_tool_python will download a fixed version of LanguageTool (LT).

There was also a inconsistency in the code when a more recent version of LT is installed in the download path:

• the package will still download the hard-coded version
• but it will use the more recent version found in the download path

Now the user can specify the LTP_JAR_DIR_PATH environment variable. If this variable is defined, the package will look for the LanguageTool jar files in this folder. Otherwise it will download LanguageTool is the download folder.

The user can also change the LanguageTool version that is downloaded:

tool = LanguageTool(language_tool_download_version="6.3")

I also took the liberty to fix some formatting.

Note that in the tests tests/test_local.bash, the sentence 'These are "dumb" quotes.' is now accepted by the 6.4 version of the LanguageTool. Using the 6.4 version, I also got a different ordering of the suggestions, so I only check the set and I am flexible on the order.

[pidefrem]

@jxmorris12 I fixed some typos, the CI should run fine now.

[jxmorris12]

thanks -- this is really helpful :)