Nextcloud versioning support added

[caronc]

Description:

Related issue (if applicable): #395 and #371. Additionally PR #429

Added ?version= value to Nextcloud URL. It will default to 21 if not otherwise specified. Those using an earlier version can identify it.

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in
# This way you can just destroy it after when it's all over.
# The below will create a directory called apprise
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@371-nextcloud-version-support
# Give it a go:
# The following will run for version 21 (default):
apprise -t "Title" -b "Body" "ncloud://{user}:{pass}@{host}"

# But you can optionally over-ride this and access the older API calls by doing the following:
apprise -t "Title" -b "Body" "ncloud://{user}:{pass}@{host}/?version=20"

[amitsax]

Wiki needs update for this fix: https://github.com/caronc/apprise/wiki/Notify_nextcloud