Fixed a typo error in Clear Saved Links

Reverted the PASTE to the old code for input, textarea (not content editable)

New Tabs are opened per link order
Saved links are not cleared automatically any more
Added context-menu to Clear Saved Links
Removed FTP support due to deprecation of FTP in Firefox
Minimum version increased to Firefox 63 (released 2018-10-23)
Disable Notification option (default false) changed to Notification (default true)
New Option page with About & Help
OOP Code Improvement

Pure CSS Navigation
Style/Code Improvement

Functions of URL MultiCopy incorporated
Added Option to disable Information Notifications but keep Error Notifications