Merge: merge client-python3 to master for version 1.0.0

[MCatherine1994]

Summary of changes on shoal-client:

• Updated to support both python2 and python3
• Removed duplicate code
• Updated to get extra verified squids from the shoal-server
• Added functional test for squids returned from shoal-server, and rank squids based on the time cost
• Removed the duplicate squids
• Added default squids to the list when choose frontier option
• Removed "DIRECT" option for frontier
• Updated default squid proxy to include the cvmfs_http_proxy in the cvmfs config file (/etc/cvmfs/default.local)
• Updated spec files to support the building of rpm package
• Added readme to pypi project description
• Updated version to 1.0.0

[MCatherine1994]

Installation requirements:

• Packages for python2: epel-release (for python-pip), python-pip, python-netifaces (needed for error: Setup script exited with error: command 'gcc' failed with exit status 1)
• Packages for python3: python3, python3-pip
• Make a directory /etc/shoal/, and copy config file shoal_client.conf to /etc/shoal/ (shoal_client.conf will be at /shoal/shoal-client/conf/shoal_client.conf if install using git method, and in /usr/share/shoal-client/shoal_client.conf if install using pip method)

[MCatherine1994]

Todo:

• [x] Update shoal_client.conf file install localtion, so shoal_client.conf will be installed at:
  • /usr/share/shoal-client/shoal_client.conf for python2
  • /usr/local/share/shoal-client/shoal_client.conf for python3 Updated Readme to let the user copy and update the file as they need
• [x] Need to check if default_squid_proxy Direct workes with frontier or not
  "DIRECT" is the keyword for cvmfs talk only and not apply to the frontier, so removed the "DIRECT" option for frontier
• [x] Consider the default cvmfs http proxy Include the cvmfs_http_proxy from /etc/cvmfs/default.local if has one

Discuss: What will be a good idea if the local squid is actually not available? Should we consider a test, or update the shoal-agent to only enable broadcast if there is an available squid (pass the test)? Answer:
Current on the shoal-agent side, only enable broadcast data with BROADCAST_ID when squid is available, so client could only get the broadcast when there is an available squid.

RPM Note: When install rpm package for shoal-client and run in python3, need to have epel-release pre-installed, otherwiser required packages "python36-netifaces" "python36-requests" won't be found