Enable updating to/from non `%ProgramFiles%` locations

Closes #13 (closed) and adds "Portable/adminless" installations

assigned to @idk

changed title from Start adding JNA stuff, for now just copied from zlatinb's but I'll need to... to {+Enable updating to/from non %ProgramFiles% locations+}

added 7 commits

• 74d5ccc4...99ef12af - 6 commits from branch master
• 73f94a12 - Merge branch 'master' into 'settable-paths'

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There's a lot of changes and I've been trying to follow what is happening, but it's tough. Can you give a summary of how the windows easy install bundle behaves before and after this MR?

Most of it is there to spot admin vs non-admin installs and react accordingly.

Before: I2P Easy install must be installed to %ProgramFiles%, and must be run using a config in %LocalAppData%. Moving either of these results in the scripts used to launch the router and the apps breaking. Some of the consequences are:

1. Installs can't be fully "Silent" they will always require at least one privilege-elevation prompt to gain access to the %ProgramFiles% directory, including during updates
2. Users who are not the admin cannot use the bundle to install I2P under their own user namespace
3. In various places, essential settings are hard-coded compounding the immovability issue

After: I2P easy install may be installed anywhere, with %ProgramFiles% replaced as a default when running without admin rights. Without admin rights, the everything goes into directories in %LocalAppData%, and with admin rights, %ProgramFiles is still used. It also allows setting the default path to the package and configuration directory by overriding environment variables before running the application. This way:

1. New installs will be able to update silently because there are no privileges required to successfully run the installer with a target the user can write to(%LocalAppData%).
2. Installation can be performed without root anywhere the user has permission to run an application, which is usually anywhere they can write unless there's a group policy.
3. No more hard-coded settings essential to the running of the router

Turns out, a TON of the stuff I did early on depended on I2P being in the same place the scripts expected it, so basically, this disentangles those expectations from the installer.

added 1 commit

• e051d409 - add use_system_colors to the prefs.js and user.js files

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added 2 commits

• b8b7a1d2 - 1 commit from branch master
• a05f3777 - Merge branch 'master' into 'settable-paths'

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added 6 commits

• a05f3777...a20b8ff4 - 5 commits from branch master
• c426b73d - Merge branch 'master' into 'settable-paths'

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merged

mentioned in commit 66864c31