Improve left panel

[tesshucom]

Webpage considerations. Related airsonic/airsonic#1804, Related airsonic/airsonic#1805, #1734.

To be honest, Airsonic's left panel is out of common sense and should be improved. Too many useless features.

• We should reconsider linking items and go back to the traditional style of opening a dedicated, separate page from that links.
  • We should stop designing to refer to all data on the top page.
  • Each feature should be considered and improved on its own page. The required view design is different for each features.
• The items that should be displayed are not determined, but should be optional for the user to select.

This Issues themselves were derived from the Web Radio topic. Web Radio is considered to belong to "Broadcast" in item classification in UPnP. In other words, like podcasts, there is nothing unnatural about having independent pages. Initially, a new page should be created that maintains the current functionality. Subsequent expansion is another matter.

[tesshucom]

Related : ##1879. There will be some fixes in v113.

[tesshucom]

Related : #2349

Starting with v113, the web and UPnP menu items will be restructured. Since Internet TV & Radio is also included in this consideration, this issue will be closed for now.

What will be done after v113 is not so much the implementation of the Left panel, but rather a comprehensive redesign of what Jpsonic will provide to users at the Top Level. Implementation will proceed with a policy of making Web pages and UPnP compatible. So everything that was going to be covered here will be included in #2349.