Add t5common package

[ajtritt]

Add a package for common operations in the Taskforce5 commons.

• A class for connecting to and interacting with Jira (Python class t5common.jira.JiraConnector)
• A framework for polling Jira for new issues, and starting workflows (commands init-db, check-jira, and mark-job)
• A class for building SLURM sbatch scripts (Python class t5common.job.SlurmJob)

Fixes #15

[oruebel]

Should the cron jobs/code for pulling data from CSBID and pushing to Jira go here too? @yonglbl @ajtritt

If yes, this can be a separate issue/pr. Just wanted to check.

[ajtritt]

Should the cron jobs/code for pulling data from CSBID and pushing to Jira go here too? @yonglbl @ajtritt

I think we should put the CSBID-specific code in its own package or subdirectory.

[oruebel]

Looks good. It would be useful to add docstrings for the public functions to make it easier for us to reuse the code when setting up new integrations.