Rewrite install dir resolution for legacy plugins

[Jule-]

Let's start fresh!

What does this PR do?

This is the rebase of my old PR #576 coming from #575 on the master branch as encouraged.
Basically I have separated bloc that was handling new app directory structure from the old one. Plus I have rewrite tests with RegExp allowing buggy forms with or without / at the end.
Plus all (hope so) code reviews from @brodybits.

What testing has been done on this change?

• new: app, app/, app/whatever
• old: src, src/, src/whatever/source, libs, libs/, libs/whatever/bin
• buggy: src/myappsomething/source, appsomething/source
  Like my original issue with: cordova-plugin-local-notifications. Try it:

$ cordova plugin add cordova-plugin-local-notification

Contextual issues and PRs raised

#577, #578, #580

[codecov-io]

Codecov Report

Merging #589 into master will increase coverage by 0.13%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #589      +/-   ##
==========================================
+ Coverage   62.11%   62.24%   +0.13%     
==========================================
  Files          17       17              
  Lines        1985     1992       +7     
  Branches      371      371              
==========================================
+ Hits         1233     1240       +7     
  Misses        752      752

Impacted Files	Coverage Δ
bin/templates/cordova/lib/pluginHandlers.js	87.64% <100%> (+0.5%)	⬆️

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[brodybits]

Can you make a couple more vars for:

• '\\' + PATH_SEPARATOR
• (\\' + PATH_SEPARATOR + '|$)

Everything else looks good now, I will merge if you fix it right. Thanks again for your efforts.

[Jule-]

Is that what you were thinking about?

[brodybits]

Merging now. Thanks @Jule- for contributing the improvements.

[Jule-]

You're welcome! 🙂👍

[brodybits]

This change is merged onto the master branch by a "squash merge", may be included on 7.1.x branch if we need it someday. I edited a few of the listed changes for extra clarity while merging.

@Jule- I noticed that the changes were proposed from your master branch. In the future you may want to propose changes from a new branch name to keep your own master branch clean; this is also better in case we merge with a merge commit.

[Jule-]

@Jule- I noticed that the changes were proposed from your master branch. In the future you may want to propose changes from a new branch name to keep your own master branch clean; this is also better in case we merge with a merge commit.

Copy that!