Update merklelib to support Python3.10

[myxie]

Issue

The version of merklelib currently stored on Pypi is not up-to-date with the repository, which means we do not have changes that make it compatible with Python 3.10 (vpaliy/merklelib#10).

Solution

We could point to the GitHub repository instead of trying for the Pypi project, but unfortunately there are outstanding issues with the setup.py that have not been remedied (vpaliy/merklelib#11).

@pritchardn has a repository that is up-to-date with the original/base repository, and we have merged a fix for the setup.py script (see pritchardn/merklelib#1).

We will use this version of the merkelib moving forward and pull it directly from GitHub when installing DALiuGE.

Testing

Confirmed the installation works as expected using pip install:

Obtaining file:///home/rwb/github/daliuge/daliuge-common
  Preparing metadata (setup.py) ... done
Collecting merklelib@ git+https://github.com/pritchardn/merklelib
  Cloning https://github.com/pritchardn/merklelib to /tmp/pip-install-h11un0nu/merklelib_cf7d9f0b4d414cabbb0e72858fad6307
  Running command git clone --filter=blob:none --quiet https://github.com/pritchardn/merklelib /tmp/pip-install-h11un0nu/merklelib_cf7d9f0b4d414cabbb0e72858fad6307
  Resolved https://github.com/pritchardn/merklelib to commit 2c69dd09a677287bb93136efcb36a86de7f4e641
  Preparing metadata (setup.py) ... done

Translator tests now pass as expected.

======== 181 passed, 27 skipped, 3 warnings in 57.71s =======

[myxie]

@awicenec may you please provide a review for this?

[coveralls]

coverage: 79.827%. remained the same
when pulling 12438d2 on myxie:dlg_modify_merkletree_install
into 3b4ef66 on ICRAR:master.