Sleipnir Browser

What's new in this version:

Bug Fixes:
- The cursor will no longer obscure text, unless that text is the same color as the cursor
- Known issue: underlines are now drawn on top of the cursor. Follow #6499 for updates
- Win32-OpenSSH 7.7 is here to stay, so we decided to fix the issue that allowed it to break mouse input
- Our caption buttons now fade like everyone else's when you hover over them
- Text copied from the File Explorer's "Copy Address" option will now be pasteable
- Every time the window was resized, we'd lose track of another GDI handle. Now, we don't
- Maximized terminal windows will finally put their tab strips right at the top of the screen. Unrelatedly, Paul Fitts called to let us know about this one weird law
- The maximize/restore button now more accurately tracks the state of the window
- Right-clicking the negative space between the tabs and the caption buttons will now open the system menu
- Some of you thought it would be a good idea to close a tab while dragging it around. I couldn't figure out why you wanted to do that, but it will at least now not do something strange..
- You can now drag and drop snippets of text onto the Terminal and it'll do roughly what you'd expect
- The keen-eyed among you may have noticed that the 6x6x6 xterm color cube was totally horked. Thanks to @j4james, this egregious sin has been corrected
- Terminal will no longer rely on PATH lookup for cmd and powershell. They ship as part of Windows, so we should know exactly where they are

Performance:
- We've added a couple fast paths to things that the profiler told us were taking more time than we expected