Many fixes, but not all

Note: fixing coding for some problems is still difficult. Please continue with feedback if that issue is not labeled as "bug" or listed in Projects. If you are interested in coding, please ask any questions regarding progress or difficulties.

Fixes:

• [Fix] mouse scroll to focus tab broken since Fx48, fix #97
• [Fix] Enter key on Address bar to open in new tab, since Fx50, fix #115
• [Fix] Avoid Bookmark Properties dialog appears as blank since Fx49, #110
• [Fix] Datetime as title for "Bookmark All Tabs…" now works for Fx44+, #65
• [workaround] Fix middle click on link get it open in the foreground if e10s turn on, #117
• [Fix] extensions.tabutils.openTabNext=1[All] not work since Fx51, #109
• [Fix] Allow open new privacy-browsing or non-e10s window when single-window mode is enabled. #98
• [Fix] Sound indicator should be located on right side of tab, #90

Please wait for AMO review and auto-update if you need to use this on Release or Beta.