[skip ci] Update start-installation.md

[skip ci] Update documentation to mention addFlash

Fixes #5232 and #5231

related to #5128

Fixes #5088: new password reset token is now generated only if previous one was already used or expired

with help of ##English on freenode :)

fixes #5244

French start-forms.md

[skip ci] Latvian translation and Russian i18n guide 

Update app templates to use bootstrap ActiveForm

[skip ci] Update README.md  instruction for install core framework.

Updated instructions for the current reality.

[skip ci] jquery .val() not .value

[skip ci] Update tutorial-template-engines.md

just fixed typo

In line 180. 
It should be .val() instead of .value.

This is my first edit.

[skip ci] Create start-hello.md

close #5214