Add "archive leagues" feature (#97)

[domwakeling]

Ability to archive leagues (since they can't be deleted), adding a new expandable 'Archive' entry in the Menu (material-ui Drawer element).

In client/src/actions/league.js

• add new action switchArchiveLeague
• add 'archived' status to existing action editLeague to ensure redux store stays in sync with Mongoose

In client/src/components/dashboard/leagueTabs/leagueTabData.js

• add data for a new 'sub-tab' in the 'settings' tab

Write new file client/src/components/dashboard/settings/forms/LeagueArchiveForm.jsx to provide UI in new 'sub-tab

In client/src/components/dashboard/settings/forms/editLeageNameForm.jsx

• add PropType validation to deal with linting errors (no change to functional code)

In client/src/components/dashboard/settings/routes.jsxand client/src/components/routes.js

• add new routes

In client/src/components/nav/Menu.jsx and client/src/components/nav/MenuLeagueItem.jsx

• refactor code for presenting leagues (which is now used twice) into separate component
• additional code to render the two lists (normal and 'archived') as appropriate

• additional code to style icons

  In client/src/components/styles/cssDashboard.js and client/src/components/styles/cssMenu.js

• additional styling rules

In server/models/league.js

• update schema/model to include 'archived' key

In server/api/auth.js

• update query method to include 'archived' value in return from Mongoose/MongoDB

In server/api/league.js

• update server methods to include 'archived' value

[domwakeling]

Change made; looks as though I had also made two further minor tweaks (which have likely been superseded in the last year!) which had not been committed/pushed.

[paulywill]

@domwakeling