feat: compression options and stack nicknames

Stack url can now be specified (if defined in the environment!) using nicknames, such as staging or production. To define the nicknames in environment add an environment variable with a prefix XCHEMALIGN_FRAGALYSIS_URL_, the script will use this to find the urls. For example the variable
XCHEMALIGN_FRAGALYSIS_URL_PRODUCTION=https://fragalysis.diamond.ac.uk
will set nickname 'production' to point to an url https://fragalysis.diamond.ac.uk (i.e. everything after the prefix in lowercase will become the nickname)

Another feature is the compression. The scipt will now handle the data compression itself (the default) and will use an existing tarball only if instructed.

USER-GUIDE.md

@@ -451,7 +451,14 @@ To use the XChemAlign uploader tool, first log in to Fragalysis and obtain the a
 Then run the upload command:
 
 ```commandline
-python -m xchemalign.uploader -i <gzipped tar file> -u <fragalysis url> -p <proposal number> -t <token>
+python -m xchemalign.uploader -u <fragalysis url> -p <proposal number> -t <token>
+```
+
+This will find the latest upload directory, compress it to a tarball, and then upload it to a given URL. If the tarball already exists, the compression step can be skipped by specifying either
+`-d` or `-c <path to custom tarball>` parameters. Instead of a full URL, a stack nickname can be used, if defined in the environment. To see the nicknames available, use the help command:
+
+```commandline
+python -m xchemalign.uploader -h
 ```