Virtual events handbook updates - 2020-08-03 - V1.17

Why is this change being made?

Virtual events handbook updates happening on 2020-08-03 for Marketing Agility project: Virtual event excellence.

List of changes (Please list high-level changes here so we can quickly know what changed in this MR):

• Add webcast reschedule and cancellation process @aoetama
• Add self-service virtual event reschedule and cancellation process. @krogel
• Add external virtual event reschedule and cancellation process. @krogel
• Add vendor arranged meetings and executive roundtables to external virtual events handbook @krogel
• Change terminology from sponsored virtual event to external virtual event everywhere that term is used for consistency. @aoetama

Author Checklist

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