Improvements for template favicon and metadata handling

[philippjfr]

Cleaning up recent PRs adding favicon and metadata handling for the basic templates.

• Bundles the favicon.ico into the panel.js distribution so it's available as a server resource and will be uploaded to NPM
• Removes default metadata

To Do:

• Update docs

@MarcSkovMadsen

[codecov]

Codecov Report

Merging #1650 into master will decrease coverage by 0.00%.
The diff coverage is 90.90%.

@@            Coverage Diff             @@
##           master    #1650      +/-   ##
==========================================
- Coverage   85.41%   85.41%   -0.01%     
==========================================
  Files         148      148              
  Lines       16837    16840       +3     
==========================================
+ Hits        14382    14384       +2     
- Misses       2455     2456       +1     

Impacted Files	Coverage Δ
panel/template/base.py	72.80% <90.90%> (-0.06%)	⬇️

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[MarcSkovMadsen]

Hi @philippjfr

Looks nice. If I can find time I will try to contribute the changes to the docs. But right now I don't if it will be today or within a week. So feel free to do it first.

The changes you have made looks nice.

I can see you have set keywords, description etc. to "". I was in doubt here. The reason why I added something is that have Panel, HoloViz etc. show up in the description, keywords etc. on several sites will make it more known by Google Search Engine as far as I understand. Thus people who use the defaults will be advertising a bit for HoloViz and Panel which is a small price to pay for a great product. But I also understand if you don't want users to "pay that price" maybe without taking an active decision.

[philippjfr]

Yeah, I get your reasoning there. Maybe I should promote more but feel like it'd be a little bit rude to insert that everywhere. Can reconsider that later. For now I'll merge.