Product improvements: opportunities page columns, notification clearing, call quality

The Close engineering team has been hard at work on some coming-soon email, task, and workflow features. In the meantime, we also took care of some miscelleneous improvements in the past 6 weeks that we wanted to let you know about.
Features & improvements:
- Opportunities page: allow customizing the columns displayed (screenshot below)
- Automatically clear missed call & voicemail notifications when you call back a contact's phone number, saving you and fellow ring group members some extra clicks.
- Nicer UI for including attachments in email, including a much larger "drop target" when you're trying to drag & drop a file to become an attachment in an email draft.
- Desktop application: call quality improvements and automatic detection & workaround for network issues preventing calling from working properly.
- In search, you can now combine multiple or-queries into a more efficient in-query. For example, you can now say 'city in (San Francisco, Berlin, Zurich)' instead of 'city:"San Francisco" or city:Berlin or city:Zurich'.
- Infrastructure upgrades: new, faster servers to make Close faster & more stable.
- Introduced the ability to pause and resume bulk actions via the API. See the developer docs.
Bug fixes:
- Missed calls to ring groups no longer result in double notifications per call.
- Explorer: Fixed issue where PNG & CSV export options didn't work in some browsers.
- Explorer: Fixed a bug where clicking on "Show Leads" would generate a wrong query when grouping by a custom field of type "Choices".
- Fixed a bug where BCC recipients weren't show in sent/received emails in Close.
- Fixed a bug where a newly added lead status wouldn't show up immediately in search filters.
- Added workaround to a Chrome 41/42 bug that prevented MacBook Pro Retina users from scrolling on lead pages when mouse cursor was focused in certain sections.
