Add term table, accomodate multiple terms, fix course.sis_id bug (#113, #117)

[ssciolla]

This PR modifies the COURSE_INVENTORYjob and the database schema as to be able to collect and store data related to multiple academic terms. Some additional details are provided in the task list below. This PR aims to resolve issues #113 and #117.

• Add migration with new term table and with a term_id column and foreign key constraint to the course table.
• Make CANVAS_TERM_ID configuration variable plural, i.e. CANVAS_TERM_IDS.
• Add function that pulls data for terms specified in the config.
• Modify get_course_data_from_api function to accept multiple terms, nest fetching process insidefor loop, and then combine all results into one course_df (ensuring that future processes will consider courses from the multiple terms specified).
• Write contents of term_df to database.
• Add migration changing the data type of course.sis_id to VARCHAR(15) and type coercion to string of those values (see issue Change data type of course.sis_id to VARCHAR #117 for details).
• Update online_meetings/canvas_zoom_meetings.py to handle multiple terms.
• Update README.

[lsloan]

@ssciolla, any idea why Codacy claims zoom_course_report is using "%s as argument"? (Which Codacy can't even display correctly!)

Can we use comments to tell Codacy (or in this case, PyLint specifically) to ignore this error for this section of code? (https://github.com/tl-its-umich-edu/course-inventory/pull/115/files#diff-9e1a06acd700cfb38555dc5980f1cdb0R163)

[ssciolla]

@ssciolla, any idea why Codacy claims zoom_course_report is using "%s as argument"? (Which Codacy can't even display correctly!)

Can we use comments to tell Codacy (or in this case, PyLint specifically) to ignore this error for this section of code? (https://github.com/tl-its-umich-edu/course-inventory/pull/115/files#diff-9e1a06acd700cfb38555dc5980f1cdb0R163)

I think that's an issue that was there before; it doesn't like the default mutable argument of []. I'm not really sure I get why it's an issue; if we agree, maybe it's something we can configure in Codacy?

[lsloan]

After discussion, the things I commented on seem to be minor issues, so I'll give my approval of this PR.

[jonespm]

I think this seems fine and will work. The only problem is that there is no indication of the term for the canvas_zoom_meetings in the csv report but I don't think this is necessary right now and this will be changed anyway with #114. Just have the one fix that should probably be made.