Version bump to address update issue

I had forgotten to update the internal version of the plugin beyond the release tag on GitHub. This is now using 2.1.1 as the version and should fix update issues.

Thanks to @FiveTeethless for the PR.

v2.1: Better legend

The legend now shows the min and max deltas in addition to the min and max temps, and also shows the color range as it pertains to the active tiles. No more generic cold-to-hot gradient bar.

v2: Full color gradients!

This release adds full color-gradient support!

Note a change in coloring behavior vs 1.x versions. Since the colors are now a full heatmap gradient, as per user feedback on the OctoPrint Discord, the colors now map to thermometer colors: blue areas are colder and red areas are hotter. Hopefully this makes for a more consistent experience.

Each tile will be shown in increasing opacity towards blue if it is cooling down and red if it is heating up. The closer the tile is to the set temperature, the more transparent it will be, and it will match the background color.

Text will also now auto-swap from black to white based on tile luminance.

Removed silly development comment

Removed the note for super-nerds relating to the pixel size of tiles vs cm dimensions.

Hotend temp added and temperature hysteresis

This release adds temperature hysteresis (the tile is considered at nominal temperature within +/- 0.3 degrees of the target value).

The hotend temp is also shown at the bottom of the panel to help prevent having to flip back to the temperature panel. Visibility of this and the average bed temperature should be configurable at some future point.

Opt into autoescaping for security reasons

As per Octoprint guidance, this prevents plugins from executing purposely or accidentally malicious HTML code into the page.

Read more here: https://community.octoprint.org/t/how-do-i-improve-my-plugins-security-by-enabling-autoescape/61067

Minor fix to plugin title

The wrong title was showing in the Plugins UI screen ("Segmentedbed" instead of "Segmented Bed") due to a bad entry in init.py. Fixed.

Less hacky code

Merged PR1 from @larrrox which improved my comments with more detail, and added a much cleaner way to loop thru the array using the reorderMatrix.

Thanks @larrrox !

Better layout with a nicer color scheme

A more well-behaved CSS/HTML layout.

77% less crappy code

This is far less of a hack and slash job now. There is still some "magic" array manipulation to reorder the tiles that, frankly, a better coder will likely laugh at. That's on the to-do list.