Use latest compatible instead of latest available for Install checkboxes

[HebaruSan]

Problems

While setting up to reproduce KSP-CKAN/NetKAN#10157 in a fake 1.9.1 instance, I noticed some problems:

• My CKAN was trying to install the latest RealismOverhaul when I clicked its Install checkbox, which isn't compatible with KSP 1.9.1, rather than the latest compatible v13.1.1 as in that issue's screenshot
• The GUI prompts that ask the user about auto-updating CKAN and auto-updating metadata are confusing. When I first switched into the fake 1.9.1 instance, I honestly could not tell what the first one was asking me about, since it didn't specify (the second one was clearer, but by then I already had to decide what to do about the first one).
• The file conflict message says "Owning Mod: TweakScale" without the version, so I had to ask the author of the issue to check what the version was, even though CKAN definitely knows the version since it's an installed module.
• Dropping SHA-1 as Stop checking multiple hashes #4135 planned to do would break importing manually-downloaded ZIP files

Causes

• Better version specific relationships at install and upgrade #4023 set the mod to be installed to GUIMod.LatestAvailableMod, which is the absolute most recent, rather than GUIMod.LatestCompatibleMod as it should have been
• ModuleInstaller.ImportFiles only checks the SHA-1, so any module with only an SHA-256 in download_hash would fail to be detected

Changes

• Now we install GUIMod.LatestCompatibleMod, so the right version will be installed on old game versions
• Now both auto-update prompts are rewritten to be hopefully easier to understand, with the parentheses removed and some newlines added for readability
  • The GUI prompt about auto-updating CKAN specifies that it is talking about updating CKAN itself
  • The GUI prompt about auto-updating metadata says that you should click Refresh once in a while if you don't auto-update and mentions the settings
• Now the file conflict kraken captures an InstalledModule instead of a just an identifier, and renders it with InstalledModule.ToString(), which includes the version, install date, and whether it was auto-installed as a dependency of another mod
• Now ModuleInstaller.ImportFiles first checks the SHA-256, then falls back to the SHA-1 if not found
  • Now Registry.GetSha1Index is renamed GetDownloadHashesIndex and includes both SHA-256 and SHA-1 hashes as keys in the dictionary it returns.
  • Registry.GetDownloadHashIndex is renamed to GetDownloadUrlHashIndex
  • Both Get*Index functions are refactored (and LINQified) to cache their calculated dictionaries in between repo updates, in case the user needs them multiple times in a row