fix(install): add property to Vue object to avoid memory leak

[johnleider]

Description

Workaround for memory leak caused by infinite global mixins being declared when in dev mode using HMR

Motivation and Context

Fix memory leak

How Has This Been Tested?

Making changes in dev mode, triggering HMR for the documentation

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any feature but make things better)

Checklist:

• The PR title is no longer than 64 characters.
• The PR is submitted to the correct branch (master for bug fixes and documentation updates, dev for new features and breaking changes).
• My code follows the code style of this project.
• I've added relevant changes to the documentation (applies to new features and breaking changes in core library)

[TravisBuddy]

Hey @johnleider,
Your changes look good to me!

View build log

TravisBuddy Request Identifier: ff01a1e0-8e6c-11e9-8722-2b49c01fe0f5

[codecov]

Codecov Report

Merging #7497 into next will decrease coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             next    #7497      +/-   ##
==========================================
- Coverage   87.19%   87.17%   -0.03%     
==========================================
  Files         326      326              
  Lines        8447     8449       +2     
  Branches     2116     2117       +1     
==========================================
  Hits         7365     7365              
- Misses        992      994       +2     
  Partials       90       90

Impacted Files	Coverage Δ
packages/vuetify/src/install.ts	0% <0%> (ø)	⬆️

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[codecov]

Codecov Report

Merging #7497 into next will decrease coverage by 0.03%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             next    #7497      +/-   ##
==========================================
- Coverage   87.19%   87.15%   -0.04%     
==========================================
  Files         326      326              
  Lines        8447     8449       +2     
  Branches     2116     2117       +1     
==========================================
- Hits         7365     7364       -1     
- Misses        992      995       +3     
  Partials       90       90

Impacted Files	Coverage Δ
packages/vuetify/src/install.ts	0% <0%> (ø)	⬆️
packages/vuetify/src/components/VSelect/VSelect.ts	93.99% <0%> (-0.43%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 52c2b7a...0c8234c. Read the comment docs.

[dsseng]

LGTM, long waited fix!

[dsseng]

need tests

Too obvious to test