[Backport 2.1] Add RewriteBase directive template in .htaccess file into pub/static folder

[ccasciotti]

Backport of pull request #13678

[magento-engcom-team]

Hi @ihor-sviziev, thank you for the review.
MAGETWO-88277 has been created to process this Pull Request

[TomashKhamlai]

@ccasciotti, please provide manual test scenario.
As far as I could understand, I have to uncomment the expression added to {web_root}/{doc_root}/pub/static/.htaccess file and replace 'magento' to the real {doc_root} where Magento was installed.

Could you please describe next steps that will demonstrate the advantages of these changes?

[ccasciotti]

@TomashKhamlai as I described in original pull request, this PR adds RewriteBase directive into .htaccess file into pub/static folder, in case the need is to install Magento code under a directory inside the web root. Setting this directive into .htaccess file in Magento root and without setting it into .htaccess under pub/static folder cause a file missing (js and css) by Apache Web Server